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The purpose of this thread is to reach a calculated dispersion for these guns which real dispersion is unknown, and without considering where and how the guns were mounted.
I will start with the following page to calculate kinetic energy (1/2 * m * V^2) per minute for some representative guns (mass of the round (M) in Kg, muzzle vel (MV) in m/s, energy (E) per minute in Mj/min and rounds per minute (RPM) ):
Gun Tables (http://www.geocities.com/CapeCanaveral/Hangar/8217/fgun/fgun-pe.html)
MG131 (unsync?): M 0.036Kg, MV 730 m/s, RPM 900 -> E 8.63
MG-FF: M 0.134Kg, MV 600 m/s, RPM 530 -> E 12.78
50"M2 (unsync): M 0.043Kg, MV 880 m/s, RPM 850 -> E 14.15
Type99(2): M 0.128Kg, MV 750 m/s, RPM 490 -> E 17.64
HO-5-2 (sync): M 0.096Kg, MV 715 m/s, RPM 750 -> 18.4
MG151/20 (sync): M 0.105Kg, MV 725 m/s, RPM 700 -> E 19.31
ShVAK (unsync): M 0.095Kg, MV 770 m/s, RPM 800 -> E 22.5
Mk108: M 0.330Kg, MV 505 m/s, RPM 600 -> E 25.24
Hispano MkII: M 0.130Kg, MV 880 m/s, RPM 600 -> E 30.2
NS37: M 0.748Kg, MV 890 m/s, RPM 250 -> E 74.06
From these values, and knowing the real dispersion of one of them (nose mounted), we can extrapolate the rest of dispersions for nose mounted guns. And the figure out how dispersion would be increased for other mountings.
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Hi Godo,
>From these values, and knowing the real dispersion of one of them (nose mounted), we can extrapolate the rest of dispersions for nose mounted guns.
Well, how that? :-)
Regards,
Henning (HoHun)
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Originally posted by HoHun
Hi Godo,
>From these values, and knowing the real dispersion of one of them (nose mounted), we can extrapolate the rest of dispersions for nose mounted guns.
Well, how that? :-)
I think he is talking about guestimating the dispersion as an educated guess is better than a generic setup.
With minor reservations, I agree with MANDOBLE in this case.
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HoHun,
While real dispersion numbers arrive for every gun and mounting, it is better to have a generic dispersion, but not so generic like current one.
Now imagine you have a "generic" gun able to shot pretty different rounds, with different muzzle vels and weights, and that "imaginary" gun has a particular ROF for every round type. We can try to calculate "good-enough-for-the-moment" dispersions based on the energy delivered of that gun per minute. For this imaginary gun, the more the energy, the more the dispersion. Now, if we can match some of the energy values per round type with the corresponding real guns and their dispersion, we can extrapolate the rest of the "now-not-so-generic" calculated dispersions for that "generic" gun.
A very basic example, you have 3 real guns, A, B and C. The corresponding kinetic energies per minute at 10MJ/min, 20MJ/min, and 40MJ/min. You already know the real dispersion of a nose mounted gun type B, lets say 4 mils. Then you extrapolate for A and C resulting into 2 and 8 calculated mils respectively.
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Hi Godo,
>While real dispersion numbers arrive for every gun and mounting, it is better to have a generic dispersion, but not so generic like current one.
Well, it won't work.
Using d ~ ROF * m * v^2.5 gives good fit for the MG FF/M, MG151/20 and MK108. However, it would make the high-velocity MK103 look like a rapid-fire blunderbuss, and the RCMGs would become laser guns.
You just can't match historical values that way.
Regards,
Henning (HoHun)
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Agree with Henning. There is no necessary relationship between gun power and dispersion; it depends on the gun mechanism and ammunition.
The Browning was never a particularly accurate gun in any calibre - the short-recoil design meant that the barrel had to move around instead of being fixed. The Hispano was reckoned to be significantly more accurate.
Mixed ammo, such as the German 20mm where the M-Geschoss and AP/HE-T rounds had very different weights and muzzle velocities, would produce considerable dispersion.
The mounting of the guns - especially wing v fuselage - had considerably more effect than the weapons. This is not only because wings are less rigid, but also because the dispersion of the entire armament system is what matters in practice, and wing-guns obviously produced greater dispersion.
Tony Williams: Military gun and ammunition website (http://www.quarry.nildram.co.uk) and Discussion forum (http://forums.delphiforums.com/autogun/messages/)
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Originally posted by HoHun
You just can't match historical values that way.
I know, I cant. Problem is that Pyro does not have historical values for every weapon and weapon mounting, so, AH is currently using a generic dispersion based only in caliber of the gun. Making dispersion a function of the energy and the placement of the weapon would give us a much better and much "rich" dispersion modeling.
And I do not pretend to calculate historical values, but "good-enough" relative values between the guns.
If kinetic energy * ROF is not good enough (I agree, but is still better than none), what other formula would you propose?
Tony, there are two threads already opened related to dispersion: one for real historical known dispersions and the other is this one. This one is to propose a mechanism to set the dispersion of guns when you dont have historical data about dispersion of these guns, but you still have accurate data about round weight, muzzle velocity and ROF.
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I'm not convinced at all if there is sense to calculate dispersion. In the case of some Russian guns (at least in the case of the 23mm), the mountings were actually designed so that there were some amount of loosenes to have dispersion built in and to increase probability of the hit. Sort of shot gun effect infact.
Shortly, dispersion of a gun depends probably much more on mounting itself than location of the gun or kinetic energy or rate of fire.
gripen
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Hi Godo,
>If kinetic energy * ROF is not good enough (I agree, but is still better than none), what other formula would you propose?
We could have a look at something like v0 ^ (1/x1) * (bore ^(1/x2) * barrel length ^ (1/x3) or something, with a modifier for mechanism type. With suitably chosen 2 > x1, x2, x3 > 1 we might be able to match the historical data and get a plausible result for the rest.
(That's just an improvisation, I haven't really checked this formula yet.)
Regards,
Henning (HoHun)
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Originally posted by gripen
I'm not convinced at all if there is sense to calculate dispersion.
Im convinced of the opposite.
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Is it possible that Pyro sent you on a wild goose chase so that you would discover on your own the futility of your argument...?
Ever consider that?
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Originally posted by Wotan
Ever consider that?
Are you really considering that?
Hohun, what is X1, X2 and X3? Is that formula based on something?
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yup...
But only he knows...
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Hi Godo,
>Hohun, what is X1, X2 and X3?
Three arbitrary parameters adjustable to match a mathematical function to historic evidence.
>Is that formula based on something?
It's based on nothing but my idea that it might match historical evidence :-)
Regards,
Henning (HoHun)
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Hi everyone,
After toying around with the data for hours, I've come up with the following formula:
dispersion% = a1 * bore% ^ 4 + a2 * barrel_length% ^ 2 + a3 * rate_of_fire% ^ 2
(All input values as percentages relative to a random reference gun with known dispersion. I picked the MG FF/M, but you get the same results whatever reference you choose.)
The exponents are arbitrary, but it was my impression that large calibre was the most significant contributor to dispersion. (You can see this in the MK108 with low barrel length and medium rate of fire).
Surprisingly, muzzle velocity didn't seem to have much impact on dispersion. Probably the primary parameter really is barrel length since it actually determines muzzle velocity.
a1, a2, a3 were determined to fit historical values for the German guns. I got a1 = 0.266, a2 = 0.837, a3 = 1.101.
The formula matches the following historical dispersion values:
MG FF/M - 1.0 mil
MG 151/20 - 1.9 mil
MK 108 - 1.5 mil
MK 103 - 2.0 mil
It extrapolates the following dispersions:
Browning 12.7 mm - 2.1 mil
Browning 7.7 mm - 3.3 mil
Hispano II - 2.5 mil
The 12.7 mm Browning value seems fine, only slightly worse than the MG151/20, which is what the 6 mil resp. 5 mil figures for wing mounted weapons of this type suggested, too.
The 7.7 mm Browning had a reputation for wide dispersion, so I think this might be OK, too :-)
The Hispano II - well, I don't know. It has a longer barrel and a larger calibre than the Browning 12.7 mm, so it's not suprising it comes out slightly worse.
Regards,
Henning (HoHun)
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What is the goal of these formulas in reference to the current gunnery model? Will it help us to increase our hit% or will the dispersion numbers resemble trying to hit the "X" ring at 100 yards with a Rumanian SKS?
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Cool, HoHun. I suppose the mounting scheme (wing/root/fuse/turret) would be a multiplicative factor overlaid on that?
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Originally posted by bustr
What is the goal of these formulas in reference to the current gunnery model? Will it help us to increase our hit% or will the dispersion numbers resemble trying to hit the "X" ring at 100 yards with a Rumanian SKS?
I think the idea is to vary the dispersion based on gun type and gun mount. I believe Pyro stated in a previous thread that what we currently have is a single amount of dispersion for everything.
Edit-- NM, I think what he actually said was as stated below, a single amount of dispersion based on caliber alone.
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The problem with both MANDOBLE's formula and HoHun's formula is this:
Originally posted by Tony Williams
The Browning was never a particularly accurate gun in any calibre - the short-recoil design meant that the barrel had to move around instead of being fixed. The Hispano was reckoned to be significantly more accurate.
They do not seem to mimic historical accuracy.
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HoHun, what do you put in "bore", caliber?
For artillery guns (ROF is not a factor), there are three points of dispersion generation or modification of dispersion:
1 - Initial detonation (quantity of explosive charge and mass of the round to move?).
2 - Momemtum applied to the barrel as the round advances (depending on the round design, also a factor of "jinking?" of the round inside the barrel is applied). Barrel lenght, projectile mass and acceleration inside the barrel may be the factors.
3 - When the round exits the barrel. suddenly, the previous conditions dissapear and the gun tends to recover its initial angle.
with these factors you achieve the dispersion of the very first shot. But for substained fire things are a bit more complicated:
A METHOD FOR ESTIMATION OF THE PROJECTILES PROBABLE ACCURACY IN THE CONTINUOUS FIRING (http://www.bjkmf.hu/bszemle2003/techn120104t.html)
BTW, your simplified system seems pretty accurate, and probably more than enough.
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Originally posted by Karnak
The problem with both MANDOBLE's formula and HoHun's formula is this:
They do not seem to mimic historical accuracy.
Of, course, if you already have the historical dispersion of a gun, why to apply any calculated one?
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What will a more accurately modeled dispersion accomplish for us? Please, I would like to understand. My personal understanding of dispersion is an M1A1 at 600yd. Fireing faster than 1 round per 2 to 5 minutes will show a dramatic variation in your dispersion ie your shot pattern.
Is our currently modeled dispersion akin to 5 rounds rapid fire with an SKS at 100yds or a National Match M1A1 5 rounds at 100yds? The M1A1 in competent hands will give a 2inch pattern during rapid fire(Pull the trigger as fast as you can). The SKS is lucky to keep all 5 rounds on the black.
Is this what we are talking here? And will your formula ultimatly give us an M1A1 or reduce us to an SKS? Sorry to use such a crude example, my math is not as elegant as yours, but I've had to shoot alot in my life.
Your earlier picture of the Me's wing guns being sighted in showed about a 6inch shot pattern at 125yds. Not bad for an automatic weapon.
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Originally posted by GODO
Of, course, if you already have the historical dispersion of a gun, why to apply any calculated one?
But we don't have the historical dispersion of the Hispano, just the note that it was more accurate than the Browning 50 cal. That is not something that your formula or HoHun's formula matched.
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Hi Karnak,
>The problem with both MANDOBLE's formula and HoHun's formula is this:
>[...]
Well, your post only serves as an example for the uselessness of unquantified truisms :-)
Bring a number, and we can talk.
Regards,
Henning (HoHun)
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Hi Godo,
>HoHun, what do you put in "bore", caliber?
Roger.
>BTW, your simplified system seems pretty accurate, and probably more than enough.
Well, when we've fed all our guns into it and still got coherent results, I'll agree :-)
Regards,
Henning (HoHun)
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Originally posted by bustr
What will a more accurately modeled dispersion accomplish for us?
Actually we have a generic dispersion based only on gun caliber. That is, all 20mm guns have the very same dispersion modeled, doesnt matter where they are placed, nor the gun type, just caliber.
As an example, AH 30mm Mk108 has greater dispersion than 20mm MG-FF that has greater dispersion than 12mm Brownings. But, historically, 50" had greater dispersion than mk108 that had greater dispersion than MG-FF.
Considering 30mm Mk108 alone, 109G10 can load a single one with 60 rounds. If we put a generic big dispersion on that gun based on its caliber, you will be lucky getting a single kill with it. You cant just spray&pray with only 60 rounds and a single gun. With a more accurately modeled dispersion, Mk108 will become a much more accurate weapon. Basically, if you aim correctly your chance of hit with few rounds will be noticeably greater than with the current model. Accurately edited and marked gunsights will be really useful tools.
Other weapons, like 50" will suffer an increase in dispersion. Spraying&Praying with them will ensure more hits for the poor aimers, but concentrating the hits on a particular spot will be harder. Buffs will not dissintegrate your plane at 800 yards any more with concetrated fire, but chances of getting scattered hits will increase.
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Hi Bustr,
>And will your formula ultimatly give us an M1A1 or reduce us to an SKS? Sorry to use such a crude example, my math is not as elegant as yours, but I've had to shoot alot in my life.
The results are given for the 100% dispersion radius measured in mil.
You can convert them into convenient units: At 100 m, 1 mil = 10 cm. That's about 4 inches at 110 yards.
For a 1 mil 100%-dispersion figure, you'll find all of the hits in a 20 cm diameter circle at 100 m range. Most of them will actually be grouped near the centre of the pattern.
I don't (currently) fly Aces High, but from what I've heard, it's my impression that accuracy will tend to be improved or at least stay the same with realistic dispersion, depending on the exact gun and mount.
Regards,
Henning (HoHun)
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Originally posted by Karnak
But we don't have the historical dispersion of the Hispano, just the note that it was more accurate than the Browning 50 cal. That is not something that your formula or HoHun's formula matched.
Hispanos being more accurate than 50s?? If you are talking about the very first shot of a single gun in a pretty fixed mounting, may be, still very hard to believe. But probably just the opposite with substained fire.
A good example would be the P38, with a single hispano and several 50" in the nose. I would like to see any comment of P38 pilots about the relative accuracy of these weapons.
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Hi Phookat,
>Cool, HoHun. I suppose the mounting scheme (wing/root/fuse/turret) would be a multiplicative factor overlaid on that?
Yes, that's my idea at the moment, at least for the more rigid mounts.
For the most wildly dispersing bomber guns, we probably have to blame the mountings alone, so it's not an universal principle though :-)
Regards,
Henning (HoHun)
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HoHun,
That was Tony William's data, not mine. I have no data on this subject other than Mr. William's books.
MANDOBLE,
I don't think you've adjusted to AH2 yet. I'm lucky to get a single hit at 800 yards with a bomber's tail gun and have not managed to "dissintegrate" a fighter at any range using a bomber's guns since AH2 was released. Bombers really had their teeth pulled.
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Hi Karnak,
>That was Tony William's data, not mine. I have no data on this subject other than Mr. William's books.
Well, it wasn't data, which is the problem :-/
It was a "soft" statement, and it doesn't worry me when one or the other soft statement contradicts a calculation.
I get nervous when they *all* contradict the calculation, though :-)
Regards,
Henning (HoHun)
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I think this is good thing! Give the weapons the advantages they had and not some generic formula.
Good Job Godo and Hohun !
Crumpp
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Originally posted by HoHun
For the most wildly dispersing bomber guns, we probably have to blame the mountings alone, so it's not an universal principle though :-)
Ah yes, that is sensible. We also have Wotan's data for some of the turrets, and that is prolly a good starting point for those.
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Originally posted by GODO
Hispanos being more accurate than 50s?? If you are talking about the very first shot of a single gun in a pretty fixed mounting, may be, still very hard to believe. But probably just the opposite with substained fire.
A good example would be the P38, with a single hispano and several 50" in the nose. I would like to see any comment of P38 pilots about the relative accuracy of these weapons.
As I've said before, the major determinant of dispersion in RL would have been aircraft movement in flight, followed by the rigidity of the gun mountings, followed by the accuracy of the gun. The first two are so significant that I don't believe that anyone would notice any differences in the third.
The trouble is that I read so much stuff that remembering where I read it is usually a problem...and I can't now recall where I read the comment about the Hispano's accuracy. I do have hard data on the accuracy of the .303 Browning as installed in the wings of the Hurricane and Spitfire; these weapons achieved 10 mils dispersion, with 75% of the shots within 5 mils. However, I'm not sure to what extent that's down to the gun, or to the mounting. Which prompts the question - does it matter, since it's the installed accuracy which counts?
A slightly later period, but this quote from 'Flying Guns – the Modern Era: Development of Aircraft Guns, Ammunition and Installations since 1945' might be of interest:
"Accuracy of the guns varies depending on the weapon and the installation. It is measured in mils (one mil equals one metre dispersion at 1,000 m). The .50 inch M3 could manage about 5 mils. The four Mk.12 cannon in the F8U were regarded as inaccurate, reportedly achieving only 12 mils (or 3.6 m at 300 m). The F 100 with four M39 cannon could get all of the shots within 8 mils and 75% within 4 mils. The M61 is capable of about 3-4 mils when internally mounted, although the centreline gunpod used in the F 4 is less rigid and can manage only 8-10 mils. "
P.S. I've just checked the gun pattern diagram for the Spitfire V included in 'Flying Guns: WW2'. This indicates the shot pattern for the guns at different ranges. I don't know how accurately they drew the dispersion circles, but the .303's scales to 0.5m at 100m, the 20mm to 0.45m.
Tony Williams: Military gun and ammunition website (http://www.quarry.nildram.co.uk) and Discussion forum (http://forums.delphiforums.com/autogun/messages/)
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Originally posted by Tony Williams
As I've said before, the major determinant of dispersion in RL would have been aircraft movement in flight, followed by the rigidity of the gun mountings, followed by the accuracy of the gun.
Tony, the aimer can follow and know accurately the movement of the aircraft inflight while looking through the sight, so, that dispersion is somewhat under control, in fact the pilot can generate that kind dispersion on purpose. Dispersion of the gun and its mounting is what the pilot cant really control.
This thread is about calculated dispersion on nose mounted guns based on some known real dispersions of nose mounted guns.
We can generalize the mountings as nose mounted / wing root mounted, outer wings mounted, manned, turret and grounded guns. A final factor would be gun batteries, where the movements of one gun can also affect the others. We can use the nose-mounted dispersion as a base to extrapolate the dispersion for the other cases multiplying it by predefined values.
IMO, we are in the right direction.
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I have 3mils value for the 75% dispersion for the nose mounted hispano (comapred to 4mils for the M2) on the P-38.
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Originally posted by phookat
Ah yes, that is sensible. We also have Wotan's data for some of the turrets, and that is prolly a good starting point for those.
Actually the turret data is completely irrelevant in the current discussion.
Here it is anyway:
(http://www.onpoi.net/ah/pics/users/334_1095886171_b24.jpg)
(http://www.onpoi.net/ah/pics/users/334_1095932891_b17.jpg)
Take the tail turret on the b17, 45ft dispersion at 600yrds. You can't really believe that would help determine the dispersion of the p51.
What makes me think this is just a goose chase to keep Mando pre-occupied is that as others have stated how secure the gun is mounted has more an impact on dispersion then anything. Not just wing vs. nose but how the gun is secured in the wing.
Look at the bomber gun dispersion. The variety is due to how they are mounted.
I doubt if Pyro will take Mando’s guesses over his own. But have at it...
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Hi Tony,
>As I've said before, the major determinant of dispersion in RL would have been aircraft movement in flight, followed by the rigidity of the gun mountings, followed by the accuracy of the gun. The first two are so significant that I don't believe that anyone would notice any differences in the third.
Actually it was possible to point the aircraft nose with very high precision. Lopez in "Fighter Pilot's Heaven" describes camera gun runs with a P-38 which shows that he was tracking the practice target with about 1 mil accuracy in the best recorded runs.
The Luftwaffe measured the accuracy of their guns, and they arrived at very different values for the different cannon, with the MG FF/M being twice as accurate as the MK103 when they were both mounted in the nose of an aircraft.
Of course, the position had an influence, too. Due to an ambiguity in the German records, I'm currently not sure if it increased from 1.9 mil to 2.5 mil for the MG151/20 or whether I have to read this as 0.95 mil to 2.5 mil, but it certainly made a difference.
(When you're mentioning dispersions, are these dispersion radii or diameters?)
>I do have hard data on the accuracy of the .303 Browning as installed in the wings of the Hurricane and Spitfire; these weapons achieved 10 mils dispersion, with 75% of the shots within 5 mils.
>Which prompts the question - does it matter, since it's the installed accuracy which counts?
For us, it matters, since the same Brownings mounted in the nose of the Mosquito will fire more accurately :-)
>P.S. I've just checked the gun pattern diagram for the Spitfire V included in 'Flying Guns: WW2'. This indicates the shot pattern for the guns at different ranges. I don't know how accurately they drew the dispersion circles, but the .303's scales to 0.5m at 100m, the 20mm to 0.45m.
Thanks! If these circles mean anything (for the Luftwaffe diagrams, they were not equal to dispersion radius, which was given as figure in the operating procedure), that would confirm that the Hispano II was slightly less accurate than the MG151/20 since the latter was expected to land all hits within 70 cm x 70 cm at that distance - slightly less than the Hispano's 90 cm circle. (Note that despite a specified dispersion of 2.5 mil, for passing the gun calibration test 3.5 mil were allowed.)
However, I'm not sure that this is a valid interpretation since the 7.7 mm guns with a 10 mil dispersion would have required a greater circle then.
Regards,
Henning (HoHun)
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Hi Butch,
>I have 3mils value for the 75% dispersion for the nose mounted hispano (comapred to 4mils for the M2) on the P-38.
Thanks! :-) Do you know whether this is the dispersion radius or the dispersion diameter?
Regards,
Henning (HoHun)
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dispersion diameter :)
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Originally posted by HoHun
(When you're mentioning dispersions, are these dispersion radii or diameters?)
If these circles mean anything (for the Luftwaffe diagrams, they were not equal to dispersion radius, which was given as figure in the operating procedure), that would confirm that the Hispano II was slightly less accurate than the MG151/20 since the latter was expected to land all hits within 70 cm x 70 cm at that distance - slightly less than the Hispano's 90 cm circle. (Note that despite a specified dispersion of 2.5 mil, for passing the gun calibration test 3.5 mil were allowed.)
However, I'm not sure that this is a valid interpretation since the 7.7 mm guns with a 10 mil dispersion would have required a greater circle then.
I measured the diameters, not the radius. You are right that the .303 figure is only half that mentioned previously, so possibly they took the 75% figure for the dispersion circles.
A figure of 4.5 mils for 75% hits for wing-mounted Hissos seems to match up reasonably well with 3 mils in the more rigid nose mounting of the P-38.
The 4 mils/75% figure for the M2 also seems to match up with the 5 mils quoted for the M3 - so we can say with some confidence that the .50 was capable of 5 mils / 100% accuracy, somewhat worse than the Hisso as I said.
TW
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Hi Tony,
>I measured the diameters, not the radius. You are right that the .303 figure is only half that mentioned previously, so possibly they took the 75% figure for the dispersion circles.
Thanks for the data, the pieces start to fall into their places now.
What's the relation between the 75% and the 100% radii? I'd tend to say it must be somewhere between 1.5 and 2.0.
Regards,
Henning (HoHun)
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Originally posted by Wotan
Take the tail turret on the b17, 45ft dispersion at 600yrds. You can't really believe that would help determine the dispersion of the p51.
I didn't say it could. What I said was that HoHun's formulas can be the basis for airframe mounted guns, and your pics can be the basis for turret-mounted guns.
Originally posted by Wotan
What makes me think this is just a goose chase to keep Mando pre-occupied is that as others have stated how secure the gun is mounted has more an impact on dispersion then anything. Not just wing vs. nose but how the gun is secured in the wing.
Look at the bomber gun dispersion. The variety is due to how they are mounted.
I think it much more likely that there are some mounts for which you can apply a formula and a multiplicative factor (airframe mounts), and some mounts which are so bad that they completely dominate (i.e. turrets). Consider Mand's picture from the beginning, with the MG-FF's. That took into account mounting, and still had low dispersion.
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Tony official data says :
4 mils for 75% and 8 mils for 100% for the M2
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Hi Butch,
>4 mils for 75% and 8 mils for 100% for the M2
OK, then I'll use the following values for 100% dispersion for re-calibrating my function:
MG FF/M - 1.0 mil
MG 151/20 - 1.9 mil
MK 108 - 1.5 mil
MK 103 - 2.0 mil
Browning 12.7 mm - 4.0 mil
Hispano II - 3.0 mil
Does that look OK to everyone?
Regards,
Henning (HoHun)
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Perhaps using 100% is misleading? Perhaps you should focus on the 75%, because while one gun may have, for example, 1.9mil 100%, it may be 1mil 75% (hypothetically).
I'd like to see what the MAJORITY of the bullets are going to land in, not what all of them will land in. All guns have their errant bullets, especially guns with high ROF. I don't want to see the 100%, because the few bad rounds are throwing the entire efficiency of the gun off.
So when people use 100% in computations, can you please include the majority (which I assume is 75% ??) as well, so we, the non-mathematically inclined, can read it and say "Hrm... the 100% is rather high, but it looks like MOST of the rounds are fairly accurate" and thus make up our own minds? Please?
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Hohun, aren't the M2 4 mils for 75%?
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Godo, that can't be right.
At normal ranges (est 300yds) the spread would be 12meters, wider than some planes' wingspans!!
M2, if I recall, was the US version of Hispano, yes?
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You're right Krusty ,having the dispersion only is not enought the distribution is needed too.
The M2 is the 0.50 I think
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Hi Krusty,
>Perhaps you should focus on the 75%, because while one gun may have, for example, 1.9mil 100%, it may be 1mil 75% (hypothetically).
I think the factor between the 75% and the 100% distribution should be fairly similar for all guns. I've simply used 2 for the calculations.
Thus, you can arrive at the 75% dispersion by simply dividing the above dispersion radii by 2.
Regards,
Henning (HoHun)
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Furthermore, a statistical model can be applied in-game to include both the 75% and 100% figures. As in, pick a random 0-100, if it is 75 or less place it randomly in the 75% ring, else place it randomly in the 75-100% ring.
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Originally posted by butch2k
Tony official data says :
4 mils for 75% and 8 mils for 100% for the M2
Thanks - that's slightly worse than I had expected.
It may be that the 100% figure is always about double the 75% one.
TW
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Originally posted by Krusty
M2, if I recall, was the US version of Hispano, yes?
The most common type of US 20mm Hispano was designated AN-M2 (to indicate that it was used by the army and the navy). So the term 'M2', in this context, refers to the .50. The next versions of both weapons were designated M3, but neither had any impact on WW2.
TW
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NOTE that they are several definition of the mil, the one used by me and in US manual is 1/1000th of a rad.
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The military definition of a mil is 1 meter width at 1000 meters distance. The same unit of measure we use today, they used back then. Mils are primarily used in for laying indirect fire weapons as it is a more accurate measurement than a degree.
IE - 360 degrees make one revolution. IIRC 1 degree = 13 something meters @ 1000 meters
6400 mils make one revolution. 1 mil = 1 meter @ 1000 meters.
Those Buff gun dispersions are using this definition.
A 3 mil dispersion will land 100 percent of its rounds in a 3 meter circle at 1000 meters if no other factors effect it.
It is definition number 1 on this page.
http://www.hyperdictionary.com/dictionary/mil
Crumpp
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Crummp that's exactly what i'm saying ;) :
1 mil = 1/1000 of a rad ("British angular mil"), you are speaking of the modern day Nato mil : 1/1600 of right angle, which are roughly equal.
There are at least a couple of definition like :
1 mil = 1/1000 of a rad (used in some us manuals)
1 mil = 1/1000 of right angle (used in Some wartime us Manuals)
1 mil = 1/1600 of right angle (Nato std)
the last two obviously being not equivalent.
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Originally posted by GODO
Im convinced of the opposite.
Do you think that the dispersion caused by kinetic energy and rate of fire is more significant than dispersion caused by mounting?
Originally posted by HoHun
Actually it was possible to point the aircraft nose with very high precision. Lopez in "Fighter Pilot's Heaven" describes camera gun runs with a P-38 which shows that he was tracking the practice target with about 1 mil accuracy in the best recorded runs.
Hm... I don't know if this kind of accuracy was reachable in the practice, the P-38 was the heaviest fighter as well as one of the most stablest and the target was probably not maneuvering. And these tests might had been done with gyroscopic gun sight.
gripen
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Some thoughts, correct me where I'm wrong:
Barrel length ->longer barrel flattens trajectory, no effect on accuracy by itself
Velocity-> has no effect on accuracy itself but combined with ROF causes decreasing accuracy
Caliber/bore-> the bigger the better when accuracy is concerned
(So firing 10 single rounds 30mm gives better result than firing 10 50Cal single rounds in 1000 meters??)
ROF-> the bigger the worse it gets when accuracy is concerned
Weapon weight->The heavier is better for accuracy
Rigidity of mounting-> Increases accuracy and helps to overcome the bad effects of high ROF.
Wing/engine mounting-> wing mounting increases dispersion and engine mounting decreases it.
Centerline/wing mounting-> in terms of ROF the center mounting is better as the countering force for recoil is directly behind the weapon and not to the side of it as in wing mounting (small effect in all...)
The uniformity of ammunition-> increases accuracy as all the ammo has same muzzle vel and weightand thus similar flight paths.
According to these assumptions the MK103 should be very accurate except when hung under a wing. But it is not? So what of my assumptions is wrong?
The MK108 has many good features but has bad trajectory and needs rigid centerline mounting to be accurate in rapid fire because of its light weight.
I'd imagine ME110 with MK108s and P38 with 50Cal and Hisso to be very accurate mountings and of course all the a/c with centerline mountings.
MG FF is still quite accurate despite its wing mount owing to its low ROF and moderate muzzle velocity. The hispano is also good despite its non-optimal mounting in Spit or Hurri's wing due to its weight and relatively slow ROF? I'd imagine the wingpod mounted MG151/20 to have quite high dispersion and very much different than if mounted centerline as in 109.
-C+
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Originally posted by Tony Williams
Agree with Henning. There is no necessary relationship between gun power and dispersion; it depends on the gun mechanism and ammunition.
The Browning was never a particularly accurate gun in any calibre - the short-recoil design meant that the barrel had to move around instead of being fixed. The Hispano was reckoned to be significantly more accurate.
For once, I disagree with you Tony. Carlos Hathcock, a famous Vietnam era Marine Sniper, once made a one-shot 2500 yard (measured) kill with a scope mounted M2 HB machine gun using standard military issue ball ammo. It's documented in the book, Marine Sniper. I don't have the ISBN or author handy--I'm at work right now. The browning short recoil system has been used for highly accurate premium grade hunting rifles, many of which are capable of 1 MOA or less accuracy.
The facts are really these: Repeatability of shot placement is affected by many factors, only one of which is the "inherent" accuracy of a particular round. One of the biggest factors is rigidity of the gun MOUNT. Airplane wings vibrate when the guns go off, adding to the vibration of the gun and all the other factors. To support your statement about the hispanos, their lower firing rate would help accuracy, since there would be more settling time for the entire mechanical system between shots. Also, since the diameter of the hispano barrel is greater, it is more rigid--and thus the amplitude of the sinusoidal vibration will be less. As has been said, there are MANY factors.
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Hi Charge,
>Barrel length ->longer barrel flattens trajectory, no effect on accuracy by itself
The barrel is subject to oscillations that negatively affect dispersion. The longer the barrel and the higher the velocity the greater the dispersion.
>The MK108 has many good features but has bad trajectory and needs rigid centerline mounting to be accurate in rapid fire because of its light weight.
Let me define "point blanc range" as the extreme distance at which you can aim the sight at the dead centre of the target and have the centre of your pattern on the target area despite the trajectory drop.
In short, point blanc is the longest range at which you can successfully pretend that you're shooting a laser gun.
Well, for fighter-sized targets, everything up to 550 m has to be considered point blanc range for the MK108.
With regard to the factors infuencing dispersion, here's what I came up with - without any physical background, but matching historical evidence:
dispersion% = mechanism_factor * (a1 * v0% ^ 3 + a2 * calibre% ^ 2 + a3 * barrel_length% ^ 4 + a4 * rate_of_fire% ^ 4)
Percentages are relative to MG FF/M.
mechanism_factor portrays the relative accuracies of the different mechanisms. I picked 0.9 for API blow back (MG FF/M, MK108) and long recoil (Hispano II), 1.0 for most other weapons, and 1.1 for short recoil (MG 151/20, Browning M2).
This is somewhat arbitrary, but a1, a2, a3, a4 change if you pick other mechanism_factors, and those I chose gave the best fit to historical data.
a1 = 0,685413726
a2 = 3,71420497
a3 = 0,490312235
a4 = 0,275524736
Here are my results:
Weapon - RL Dispersion (mil) - Calculated Dispersion (mil)
MG FF/M: 1,0 - 1,00
MK 108: 1,5 - 1,52
MG 151/20: 1,9 - 1,86
MK 103: 2,0 - 2,04
Hispano II: 3,0 - 2,95
M2: 4,0 - 4,04
0.30": 5,0 - 4,24
As you can see, the fit is quite good (+/- 2% accuracy) except for the 0.30" Browning. I've to admit that I've only guessed the "RL" accuracy, so the 16% deviation there doesn't seem that bad either.
Regards,
Henning (HoHun)
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Hi Rshubert,
>The browning short recoil system has been used for highly accurate premium grade hunting rifles, many of which are capable of 1 MOA or less accuracy.
I don't really see a contradiction here as the single-shot accuracy of a weapon is way better than rapid fire accuracy of the same weapon.
The effects you're describing seem to confirm our idea that mounting weapons in aircraft is not good for their accuracy ;-)
>As has been said, there are MANY factors.
No doubt about that :-)
Regards,
Henning (HoHun)
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Originally posted by rshubert
For once, I disagree with you Tony. Carlos Hathcock, a famous Vietnam era Marine Sniper, once made a one-shot 2500 yard (measured) kill with a scope mounted M2 HB machine gun using standard military issue ball ammo. It's documented in the book, Marine Sniper. I don't have the ISBN or author handy--I'm at work right now. The browning short recoil system has been used for highly accurate premium grade hunting rifles, many of which are capable of 1 MOA or less accuracy.
First, I entirely agree that accuracy is a complex issue and is affected by many elements. The key point is consistency: the ammunition has to perform in exactly the same way from shot to shot, so does the gun, so does the mounting. Precision in manufacture of the gun and ammunition is a vital element.
I doi not doubt that the Browning short-recoil action can be made to perform well, if made very carefully with precision in mind. But precision means extremely tight tolerances, which is just what you don't need in a military weapon, since that reduces reliability and very likely also (in a machine gun) rate of fire. The well-known facts that the Kalashnikov is more reliable than the M16, but less accurate, are not unconnected.
I believe that Hathcock's gun was modified in more ways than just having a scope added, although I've never been able to discover the details. But I do know that Hathcock himself admitted that a fair amount of luck was involved with that kill. Even if the gun was perfectly accurate and precisely aimed, the accuracy standard of the military grade .50 ammo was such that most shots would have missed such a small target at such a long range. The accuracy standard of the ammo fired in modern .50 cal rifles is much higher.
Tony Williams: Military gun and ammunition website (http://www.quarry.nildram.co.uk) and Discussion forum (http://forums.delphiforums.com/autogun/messages/)
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Guys please stop trying to argue that the accuracy of single, expertly aimed, carefully crafted, high power scope assisted 50 caliber shots from highly modified long/heavy barell weapons fired from stable positions and conditions on the ground has any bearing or relevancy on the accuracy of rapid fire, short/light barrel, 50 cals aimed by unmagnified sights and fired from the rather flexible wings of vibrating, turning, accelkeratin flying airplanes in a very high drag high airspeed enviorment...
OK?
Please....
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i have NO knowledge whatsoever on this topic but a few thing have stood out.. first this:
Originally posted by Wotan
Take the tail turret on the b17, 45ft dispersion at 600yrds. You can't really believe that would help determine the dispersion of the p51.
there is NO way we have this "model" in AH. not even close. if that is RL then we have "lazer guns" as many times said on bombers.
i KNOW this has been brought up as a gameplay discussion, the bombers fire more accuratly than RL because of thies vulnerabliity in the game withough giant formations like RL. problem is now a formation now fires on you with the accuracy of the "gameplay" consideration.
also
Originally posted by HoHun
The formula matches the following historical dispersion values:
MG FF/M - 1.0 mil
MG 151/20 - 1.9 mil
MK 108 - 1.5 mil
MK 103 - 2.0 mil
It extrapolates the following dispersions:
Browning 12.7 mm - 2.1 mil
Browning 7.7 mm - 3.3 mil
Hispano II - 2.5 mil
if these calculations are correct, then whay are the hispanos with the highest "dispersion" more a stable and accurate platform in AH than the 30mm which this data shows to be much more "accurate"
if i am reading this data correctly.
thank you for your time
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I think that Henning maybe needs to look at that formula. We've seen info from RL earlier in the thread which shows that the Hisso was more accurate than the .5 Browning (4 mils v 5 mils, IIRC)
TW
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Originally posted by JB73
i have NO knowledge whatsoever on this topic but a few thing have stood out.. first this:
there is NO way we have this "model" in AH. not even close. if that is RL then we have "lazer guns" as many times said on bombers.
i KNOW this has been brought up as a gameplay discussion, the bombers fire more accuratly than RL because of thies vulnerabliity in the game withough giant formations like RL. problem is now a formation now fires on you with the accuracy of the "gameplay" consideration.
also
if these calculations are correct, then whay are the hispanos with the highest "dispersion" more a stable and accurate platform in AH than the 30mm which this data shows to be much more "accurate"
if i am reading this data correctly.
thank you for your time
Pyro has or has the book where that data comes from. These were ground tests btw. I would imagine (could be wrong) that dispersion was worse in flight (air stream, aircraft vibration etc...)
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Hi Tony,
>I think that Henning maybe needs to look at that formula.
JB was quoting the old results which I provided without the additional data points for Hispano II and Browning M2 :-)
The new formula gives more accurate results.
Regards,
Henning (HoHun)
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Hi again,
While I'm at it:
Firepower per barrel in MW:
MK 108: 5,03 MW
MK 103: 4,08 MW
NS-37: 2,17 MW
MG 151/20: 1,27 MW
Hispano V: 1,23 MW
VYa-23: 1,20 MW
Hispano II: 1,06 MW
37mm M4: 0,91 MW
20mm Ho-5: 0,71 MW
20mm Type 99-2: 0,63 MW
20mm Type 99-1: 0,52 MW
MG-FF: 0,78 MW
Berezin B-20: 0,64 MW
Ho-1 / Ho-2: 0,64 MW
20mm ShVAK: 0,64 MW
MG 151: 0,44 MW
12,7mm UB: 0,37 MW
,50 Browning M2: 0,28 MW
MG 131: 0,21 MW
Ho-103: 0,18 MW
12,7mm Scotti: 0,14 MW
Breda-SAFAT: 0,14 MW
Browning ,303: 0,09 MW
MG 17: 0,09 MW
Regards,
Henning (HoHun)
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And that chart is meaningless since the hispano is obviously the far suerior weapon to MG151/20 in AH. Not to mention that VYa-23 is vasty better than both. Also the AH Shvak is equal to MG151/20.. :)
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Hi Grünherz,
>And that chart is meaningless since the hispano is obviously the far suerior weapon to MG151/20 in AH. Not to mention that VYa-23 is vasty better than both. :)
Well, the AH team pointed out they're open for suggestions :-)
Here's another interesting chart, showing energy density for fighter batteries based on the dispersion values I posted:
MK 108 ( 1 barrel, 5029 kW): 300 m - 5929/494 kW/m^2; 600 m - 1482/124 kW/m^2; 900 m - 659/55 kW/m^2
MK 103 ( 1 barrel, 4080 kW): 300 m - 2706/225 kW/m^2; 600 m - 676/ 56 kW/m^2; 900 m - 301/25 kW/m^2
MG 151/20 ( 2 barrels, 2536 kW): 300 m - 1864/155 kW/m^2; 600 m - 466/ 39 kW/m^2; 900 m - 207/17 kW/m^2
Hispano II ( 2 barrels, 2123 kW): 300 m - 901/ 75 kW/m^2; 600 m - 225/ 19 kW/m^2; 900 m - 100/ 8 kW/m^2
MG-FF ( 3 barrels, 2339 kW): 300 m - 6204/517 kW/m^2; 600 m - 1551/129 kW/m^2; 900 m - 689/57 kW/m^2
,50 Browning M2 ( 8 barrels, 2271 kW): 300 m - 376/ 31 kW/m^2; 600 m - 94/ 8 kW/m^2; 900 m - 42/ 3 kW/m^2
Browning ,303 (25 barrels, 2188 kW): 300 m - 232/ 19 kW/m^2; 600 m - 58/ 5 kW/m^2; 900 m - 26/ 2 kW/m^2
As a guide to this chart: These values are absolut power density so that they can be easily compared. For example, it's evident that at each range, the MK108 is more lethal at the rim of its pattern than the 12.7 mm Browning M2 eight-gun battery is in the centre of its pattern.
Regards,
Henning (HoHun)
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Hi again,
Here the results of my calculations.
I didn't have a barrel length for the MG17 or the Berezin B-20, so they're not included in the list.
In general, I've got to say that there were few surprises in the list.
It's worth noting that the MG FF/M and the Browning .303 did indeed define the opposite ends of the scale and all additional guns came in between 1,5 and 3,4 mil dispersion.
MG-FF: 1,0
MK 108: 1,5
20mm Type 99-1: 1,5
20mm Type 99-2: 1,5
Ho-1 / Ho-2: 1,5
12,7mm Scotti: 1,6
Breda-SAFAT: 1,7
MG 131: 1,7
20mm Ho-5: 1,9
MG 151/20: 1,9
MK 103: 2,0
20mm ShVAK: 2,0
Hispano V: 2,1
37mm M4: 2,1
Ho-103: 2,2
VYa-23: 2,5
12,7mm UB: 2,7
Hispano II: 3,0
NS-37: 3,3
MG 151: 3,4
,50 Browning M2: 4,0
Browning ,303: 4,2
Regards,
Henning (HoHun)
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Why the difference between the MG-FF and the Type 99-1? They were very similar versions of the Oerlikon FF.
Tony Williams
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Hi Tony,
>Why the difference between the MG-FF and the Type 99-1? They were very similar versions of the Oerlikon FF.
Oops. I mistook the total length of the gun for the barrel length :-)
So it is:
20mm Type 99-1: 1,0
Regards,
Henning (HoHun)
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Hi again,
I just found an interesting comment on the effectiveness of 0.303" guns:
"Three Fulmars of 809 Squadron expended 18,000 rounds on a BV 138 without inflicting any obvious damage." =8-O
(David Brown, Profile Aircraft 254, "Fairey Fulmar Mks I & II")
Regards,
Henning (HoHun)
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Here is some food for thought.
Enjoy.
(http://www.onpoi.net/ah/pics/users/503_1098907811_190vunerability1.jpg)
(http://www.onpoi.net/ah/pics/users/503_1098907857_190vunerability2.jpg)
(http://www.onpoi.net/ah/pics/users/503_1098907899_190vunerability.jpg)
Crumpp
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An interesting report. It does emphasise the difficulty of shooting down even fighters (let alone bombers), even with 20mm Hispanos, as long as they were strongly made and well protected.
In view of the previous thread about whether or not bullets could be deflected from an aircraft's skin it's interesting to read that:
"The smaller calibre [i.e. .303 and .5] incendiary munitions will either be broken up or deflected away before reaching the fuel tanks"
and:
"The angle of the fuselage with the line of attack is 6 degrees and this gives 0.303" B. Mk VII and 0.5" B. Mk.II no chance of causing a fire. These ammunition will be for the most part deflected or broken up on the 19 s.w.g. fuselage skin."
and:
"The angle of the engine cowlings and their material is such that all ammunitions will be deflected away without damage from this angle of attack."
Clearly, deflection off the skin was not such a rare event.
Tony Williams: Military gun and ammunition website (http://www.quarry.nildram.co.uk) and discussion
forum (http://forums.delphiforums.com/autogun/messages/)
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Tony,
Do you have some kind of numbers how accurately the pilots could normally aim at ranges above 300m? I have been under impression that some amount of dispersion is a good feature and it actually improves probability of the hit at long range.
gripen
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You didn't ask me but don't be offended if I tell you about my thoughts:
IMO there are two (or three) kinds of dispersion basically: pilot induced and platform/gun induced dispersion.
When fired from a jig the gun has its own dispersion depending on the ammo and barrel length etc.
In flight this is added to platform induced dispersion which is caused by mounting, vibration, a/c instability etc.
Then all this is added to pilot induced dispersion which is presenting the ability of the pilot to keep the hits in center of the target. So the resulting dispersion may be huge or small depending on these factors.
Considering ie. the dispersion of 8x50Cal in 300yds the combination of these factors added with a mediocre pilot would produce a considerably big dispersion pattern itself which would cause a high probability of a hit but a low probability of sufficient effect etc. So it is debatable if it would be advisable to add any convergence or elevation dispersion to guns.
The other example could be a 109F with 15mm cannon and two small caliber MGs on the cowling. I'd imagine that combination to be very accurate but in a hands of a mediocre shooter the large pilot induced dispersion would render the weapon platform to be very ineffective.
So there are many things that affect the effectiveness of a gun platform. For example, considering the 50Cal example above, on personal level the pilots could consider their weapon effect to be quite low but statistically the higher hit probability could be considered good considering the higher probability of damage caused to more a/c, than less enemy a/c that are verifiably destroyed immediately after firing.
Just a thought...
:)
-C+
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Originally posted by gripen
Tony,
Do you have some kind of numbers how accurately the pilots could normally aim at ranges above 300m? I have been under impression that some amount of dispersion is a good feature and it actually improves probability of the hit at long range.
Not specifically - although the Luftwaffe reckoned that only between 2% and 5% of their shells hit the targets, which gives you some idea of the general accuracy of fire. And the Luftwaffe's targets were usually large bombers.
Whether dispersion is a good thing or not depends on how effective each individual hit would be. The less destructive the projectiles, the more important it is to concentrate their fire to gets lots of hits in one area. Which basically means: MGs = concentrate, cannon = disperse (to some extent).
TW
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Not specifically - although the Luftwaffe reckoned that only between 2% and 5% of their shells hit the targets, which gives you some idea of the general accuracy of fire. And the Luftwaffe's targets were usually large bombers.
Combine the small percentage chance of hitting a fighter with the small chance your 20mm will do fatal damage and it's a wonder anyone was shot down in WWII.
"Filling the windscreen with enemy" certainly was sound advice and very practical advice.
Clearly, deflection off the skin was not such a rare event.
It seems to be a fairly common event. It is interesting that the Fuel tanks on the FW-190 have no armour protection surrounding them.
The tanks themselves are self-sealing. The compartment they are mounted in is not armoured. Once a bullet penetrated the skin of the A/C there would be very little metal past the compartment walls. The tanks themselves are held in place by webbing straps.
Yet from the rear no .50 cal or .303 could damage the tanks even from 6 degrees off center.
Crumpp
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Hi Charge,
Good comments! :-)
>IMO there are two (or three) kinds of dispersion basically: pilot induced and platform/gun induced dispersion.
>When fired from a jig the gun has its own dispersion depending on the ammo and barrel length etc.
The dispersion values for the Luftwaffe guns at least are for the gun mounted in the airframe and the airframe jacked up on a ground range. (I assume the same is true for the US figures.)
German engineers pointed out that experience showed this gave a larger dispersion than shooting the same guns in flight.
I figure the jacked-up airframe was free to oscillate in the rigid mounting between the jack-up points, while the airborne airframe wasn't free to oscillate in the same manner because it was "suspended" by dynamic lift acting continously over the entire wing span.
>In flight this is added to platform induced dispersion which is caused by mounting, vibration, a/c instability etc.
>Then all this is added to pilot induced dispersion which is presenting the ability of the pilot to keep the hits in center of the target.
I'd combine both aircraft instability and pilot-induced dispersion into one factor because the instability can be considered an aspect of controllability.
At high speeds, most aircraft can be expected to be quite stable and well-controllable in level flight while at low speed inertia can overcome the damping forces more easily.
As an example for pilot-induced dispersion, an experienced USAAF pilot who had done countless test firing runs to determine the optimum damping factor for the LCOS pipper had an optimum aiming error of about 1 mil during a tracking run. (He was flying a P-38.)
>So there are many things that affect the effectiveness of a gun platform. For example, considering the 50Cal example above, on personal level the pilots could consider their weapon effect to be quite low but statistically the higher hit probability could be considered good considering the higher probability of damage caused to more a/c, than less enemy a/c that are verifiably destroyed immediately after firing.
After the first phase of WW2, the Luftwaffe analysed these factors, too, though with an eye on the MG vs. cannon question. They decided for cannon because they considered it much better to bring down an aircraft down immediately over the combat area. Damaged aircraft often made it home and could be repaired, or at least cannibalized, and even if the crew had to bail some time after receiving damage, they would often make it back into friendly territory before having to bail, meaning they would soon be back in the air and fighting against the Luftwaffe again.
Of course, this doesn't tell us anything about dispersion, but it suggests that it's better to hit a couple of aircraft decisively than to light or medium damage a larger number of planes.
Regards,
Henning (HoHun)
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Originally posted by Tony Williams
Not specifically - although the Luftwaffe reckoned that only between 2% and 5% of their shells hit the targets, which gives you some idea of the general accuracy of fire. And the Luftwaffe's targets were usually large bombers.
Whether dispersion is a good thing or not depends on how effective each individual hit would be. The less destructive the projectiles, the more important it is to concentrate their fire to gets lots of hits in one area. Which basically means: MGs = concentrate, cannon = disperse (to some extent).
Well, if the accuracy of aiming was in that level, the LW would probably have benefitted from larger dispersion and higher velocity AC guns.
Regarding AH, a nice addition could be a film viewer which could calculate error of the aiming afterwards from the film and which could show a correct aiming point. I think such thing could improve players shooting abilities as well as it could give some data how accurately people can shoot in this game.
gripen
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Hi Tony,
>Not specifically - although the Luftwaffe reckoned that only between 2% and 5% of their shells hit the targets, which gives you some idea of the general accuracy of fire. And the Luftwaffe's targets were usually large bombers.
According to the documents I have seen, the numbers were either 5% as a rule of thumb (against bombers), or more specifically:
At 500 m against a four-engined bomber:
MG151/20: 9,1%
MG213: 10,0%
MK108: 8,3%
MK103: 10,0%
MK412: 10,0%
MK214: 10,5%
Regards,
Henning (HoHun)
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Hi Tony,
>Not specifically - although the Luftwaffe reckoned that only between 2% and 5% of their shells hit the targets, which gives you some idea of the general accuracy of fire. And the Luftwaffe's targets were usually large bombers.
To get 10% hits at 500 m against a B-17 as the Luftwaffe expected, you'd need about 14 mil aiming dispersion.
To get 5% hits, you'd need 22 mil aiming dispersion.
The B-17 wingspan at 500 m equals 63 mil.
My conclusion is that the Luftwaffe based its figures for attacks on bomber formations on a more difficult firing solution than found in a straight six approach :-)
>Whether dispersion is a good thing or not depends on how effective each individual hit would be.
Actually, dispersion is as likely to make a correctly aimed shot miss the target as it is to make an incorrectly aimed one hit the target. It would only help against systematic aiming mistakes, such as always aiming high, because some projectiles would scatter low and hit. Still, even more would scatter left, right and up and miss.
Regards,
Henning (HoHun)
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Originally posted by HoHun
Actually, dispersion is as likely to make a correctly aimed shot miss the target as it is to make an incorrectly aimed one hit the target. It would only help against systematic aiming mistakes, such as always aiming high, because some projectiles would scatter low and hit. Still, even more would scatter left, right and up and miss.
Hi Henning,
Well, it's rather like the shotgun principle - you stand more chance of scoring hits with a wide dispersion shotgun than you do with a rifle. They crucial question is the amount of damage a single hit can do.
At one point the RAF was certainly interested in setting their wing-mounted Hispanos to diverge slightly, as the cone of dispersion for the guns would still have overlapped to ensure hits with accurate shooting.
Tony Williams: Military gun and ammunition website (http://www.quarry.nildram.co.uk) and Discussion forum (http://forums.delphiforums.com/autogun/messages/)
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Hi Tony,
>Well, it's rather like the shotgun principle - you stand more chance of scoring hits with a wide dispersion shotgun than you do with a rifle.
The shotgun comparison is misleading here because the shotgun fires multiple projectiles while the rifle fires a single one.
Comparing two rapid-fire weapons, though, both fire multiple projectiles.
Assuming that we have two different rapid-fire weapons of different gun-inherent dispersion and gun-inherent as well as aiming dispersion being Gaussian, that means that the gun with higher gun-inherent dispersion will always have a higher total dispersion, though less than the sum because the random factors involved will compensate each other to some amount.
So, an inaccurate weapon will make inaccurate aiming only worse. With regard to random aiming errors, nothing is gained from having a higher dispersion weapon.
Regards,
Henning (HoHun)
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Actually the shotgun comparison is fully valid. The AC weapon actually sends bursts of projectiles and these disperse around aimed point depending on dispersion. Therefore the weapon with larger dispersion has better probability to hit.
HoHun's logic assumes that the every projectile is aimed individually.
gripen
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Butch made this post on his AAW II forum.
Here are the results of a lenghty research into dispersion data, which is quite hard to come by...
The data is based on 100% diameter dispersion with 1 mil = 1/1000th of rad, the kind of mount is precised next to the weapon. 75% dispersion diameter is supposed to be half the 100% diameter which seems quite true for most weapons, this value is provided when quoted in the source (M2 data for instance).
We can clearly see the impact of the wing mounting compared to engine mounting, the later seems to have absorbed recoil and vibration much better... indeed dispersion is at least 2 times greater with wing mounted weapons.
Engine mount are the most efficient but nose mounting or cowling mounting does not provide the same amount of precision the mount being much more prone to vibration it seems.
Note that US data on the M2 is confusing since the reference data comes from a P-38 nose mounted M2, but the US manuals use the same dispersion data for wing mounted weapons. Either the P-38 mounts are really up to no good or the manuals make a wrong assumption when it comes to wing dispersion. I tend to believe the later, i think the wing mounted M2 would have had a dispersion of at least 12mils and probably more.
If you quote this data on other sites/bbs please precise the source being AAW. TIA
H means Height (or max dispersion diameter) as i previously used vertical and lateral dispersion values.
D means distance.
Units are metric.
German Weapons
-----------------------
MG-17 Cowling mounted (Bf 109F-2 / Bf 109F-1 actual tests)
H = 0.60 / 0.8 m
D = 100 m
R/D = 60/10000 80/10000
= 6 mils / 8 mils
MG-131 Cowling mounted (Fw 190A - theorical max)
H = 1m
D = 100m
H/D = 100/10000
= 10 mils
MG-151/15 Engine mounted (Bf 109F-2 actual test)
H = 0,35 m
D = 100 m
H/D = 35/10000
= 3.5 mils
MG-FF Engine mounted (Bf 109F-1 actual test)
H = 0,2 m
D = 100m
H/D = 20/10000
= 2 mils (very tight patern)
MG-FF Wing mounted (Bf 109E-3 actual test)
H = 0,35 m
D = 100m
H/D = 35/10000
= 3.5 mils
MG 151/20 Engine mounted (Bf 109G-6 - theorical max)
H = 0.3m
D = 100m
H/D = 30/10000
= 3 mils
MG 151/20 Wing mounted - inner (Fw 190A - theorical max)
H = 0.7m
D = 100m
H/D = 70/10000
= 7 mils
MG 151/20 Wing mounted - outer (Fw 190A - theorical max)
H = 0.8m
D = 100m
H/D = 80/10000
= 8 mils
MK 108 Engine mounted (Ta 152 - therorical max)
H = 0.35
D = 100m
H/D = 35/10000
= 3.5 mils
Allied Weapons
------------------
M2 Nose mounted P-38 (USAAF 1944 Gunnery manual)
H = 1.88 m
D = 229 m
H/D = 188/22900
= 8.2 mils (75% = 4.1 mils)
Hispano 20mm Nose mounted P-38 (USAAF 1944 Gunnery manual)
3 mils 75%
6 mils 100% assumed
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Hi again,
Here's an illustration for the change in hit probability due to different dispersions:
http://www.x-plane.org/users/hohun/Dispersion.png
(You'd lay the target silhoutte flat on the zero plane.)
For the example, the higher dispersion weapon has 120% of the dispersion of the lower dispersion weapon. The central peak rises right at the aiming point.
(Going out from the aiming point, you move vertically and horizontally away from the target.)
Everything greater zero indicates an advantage for the lower dispersion weapon, everything below zero an advantage for the higher dispersion weapon.
As you can see, decreasing dispersion yields markedly increased hit chances around the aiming point at the cost of slightly decreased chances relatively far from the aiming point.
If you increase the difference in dispersions, the peak becomes flatter, so the advantage of the low-dispersion weapon at the aiming point becomes less pronounced. However, at the same time the peak grows in area, and the higher dispersion weapon has an advantage only further out from the aiming point, and that advantage is even less pronounced than that of the low-dispersion weapon at the peak.
By the way, the total difference in hit probabilities is zero. That's the reason the peak is always much more pronounced than the "moot", and that the moot becomes less significant as it moves outwards - the moot covers a larger area, but has the same volume as the peak.
Regards,
Henning (HoHun)
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Well, HoHun has created a beautiful chart again, but this issue is very easy to understand with a simple example of two shotguns, no calculations or beautiful charts needed. The first one has dispersion which results 100% of projectiles within 0,5 m from aimed point at certain range and the second shotgun has dispersion which results 100% of projectiles within 1,5 m from the aimed point at same range. Let's assume that the target is a round plate with diameter 1 m and ammunition used is salt loaded ie there is almost infinite number of projectiles, in addition we assume that just one hit is needed to destroy target.
Let's assume that accuracy of aiming is such that in the 100% of the cases aimed point is within 1,5 m from the center of the target so the first shotgun won't get hits in every case but the second will get hit in every case.
gripen
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Originally posted by gripen
Actually the shotgun comparison is fully valid. The AC weapon actually sends bursts of projectiles and these disperse around aimed point depending on dispersion. Therefore the weapon with larger dispersion has better probability to hit.
HoHun's logic assumes that the every projectile is aimed individually.
gripen
Indeed... except of course that we, HoHun as well are speaking about aimed bursts here, not just pushing your luck.
Therefore the weapon with larger dispersion has better probability to hit.
It has more chance to hit the target at least one time, and at the same time much more rounds will MISS the target in case of a similiarly well aimed burst.
You appear to propagate that larger dispersion is actually good.:eek: I am left to wonder why then EVERYONE in the end tried to minimise dispersion, instead of increasing it. Using cannons instead of batteries of MGs was on this track, too. A single cannon shell concentrated the power of all those MG bullets in one single place; goal being zero dispersion if you like.
Large dispersion makes one or two flashes on the target every time, which is fairly irrelevant in itself as an effect. Most of your ammo is wasted, even if you do everything right, and the final destructive effect under a given time is always LESS than with tightly grouped hits. The latter is the goal, to kill the enemy not just to score a few hits on him and be happy about it.
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Originally posted by Kurfürst
Indeed... except of course that we, HoHun as well are speaking about aimed bursts here, not just pushing your luck.
If we assume that aiming is allways perfect, then the less dispersion is better. But as noted above, for one reason or another only 2% of projectiles shoot by an average LW pilot actually hit something (I found a page (http://freepages.military.rootsweb.com/~josephkennedy/German_Pilot_Perspective.htm) which claims that number comes from gun camera film analyses). So it appears that 1 mil accuracy of aiming as claimed by HoHun above seems to be more or less science fiction.
Originally posted by Kurfürst
You appear to propagate that larger dispersion is actually good.:eek:
Actually I believe that some amount of dispersion is good and I know that in some cases dispersion is purposedly "built in" to the mounting.
Another thing to note is that higher velocity of the projectile increases accuracy of the aiming because less lead is needed in the deflection shooting. This means that long barrel might improve accuracy despite it might cause larger dispersion.
gripen
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Hi Kurfürst,
>It has more chance to hit the target at least one time, and at the same time much more rounds will MISS the target in case of a similiarly well aimed burst.
That's exactly the point :-)
The shotgun example is misleading only if you consider "something hit the target" as 100% hits.
However, once you ask "How many pellets actually hit?", you'll see that if, for example, the shotgun cone is three times as large as the target, you're hitting only with an average of 11% of your pellets if your random aiming error is smaller than the dispersion.
Exchange your shotgun for one with two times the dispersion of the target size, and you'll hit with 25% of your pellets on the average. However, the permissible random aiming error drops to just 44% of the area it had before because of the smaller shotgun cone.
This leads to the following situation:
Dispersion Pellets Hit Permissable Error Total Hits
3 * Target Area 11% 100% 11%
2 * Target Area 25% 44% 11%
Both shotguns give an identical total hit percentage.
The more accurate your aim is, the greater the benefit from a small dispersion because you don't get into the far-off-target area where the larger dispersion weapon has an advantage.
If you consider the aiming errors random, there's no total advantage for the larger dispersion weapon at all because random errors are centered at the correct aiming point, and large dispersion gives you a big disadvantage there.
That's what's shown in my graph.
You can see that the only way to gain a benefit from a large-dispersion weapon would be to avoid aiming at the correct aiming point and stay in the areas around it. Of course, that's a bad idea as even a large-dispersion weapon will be more lethal if you aim at the correct aiming point, and to avoid hitting it, you'd have to know where it is, which is the practical difficulty in air-to-air gunnery.
(The only situation where one might expect a small benefit from a large-dispersion weapon could be with wing-mounted weapon, which systematically miss the aiming point at distances short of and beyond convergence. Systematical really is the keyword here.)
Regards,
Henning (HoHun)
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Originally posted by HoHun
You can see that the only way to gain a benefit from a large-dispersion weapon would be to avoid aiming at the correct aiming point and stay in the areas around it. Of course, that's a bad idea as even a large-dispersion weapon will be more lethal if you aim at the correct aiming point, and to avoid hitting it, you'd have to know where it is, which is the practical difficulty in air-to-air gunnery.
Exactly. The aiming skills of the great majority of WW2 fighter pilots were known to be atrocious, and the greater the angle of deflection, the worse they were. They consistently uinderestimated the lead required so a tight dispersion setup would miss almost every time unless they were at short range and 6 o'clock. That's why the extra dispersion was useful - at least they should get SOME hits which might do some damage.
I think that the parameters may well have changed with the introduction of the gyro gunsight in 1944. This greatly improved the hit probability of the average pilot and probably made concentration of fire more effective.
Tony Williams: Military gun and ammunition website (http://www.quarry.nildram.co.uk) and Discussion forum (http://forums.delphiforums.com/autogun/messages/)
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Hi Tony,
>The aiming skills of the great majority of WW2 fighter pilots were known to be atrocious, and the greater the angle of deflection, the worse they were.
That might be true of some air forces, but other air forces, like the US Navy (oops :-) or the Luftwaffe put considerable emphasize on training their pilots in deflection shooting. The rest is von Clausewitz' "friction" - in war, the simplest thing becomes very difficult.
As I already mentioned, USAF tests documented a tracking accuracy of 1 mil for an experienced pilot. That's the potential of the man-machine interface in a controlled environment.
>They consistently uinderestimated the lead required so a tight dispersion setup would miss almost every time unless they were at short range and 6 o'clock. That's why the extra dispersion was useful - at least they should get SOME hits which might do some damage.
Well, if you picture the effect of insufficient lead, you'll see that you'll quickly lag far behind the target with the entire pattern at even minor estimation errors. A 20% error in range estimation against a target at 250 m, travelling at 100 m/s, will result in the aiming point being 6 m off. An 10 mil diameter dispersion will result in the 100% border being just 1.25 m closer to the target than a zero-dispersion shot, and only 0.625 m closer than a 5 mil dispersion weapon. (Successful deflection shots were most likely at short range anyway, where dispersion wasn't a great factor yet.)
A larger dispersion might be useful, though, to fill in the gap between the two patterns of wing guns at ranges out of convergence, which was an additional ballistic problem the RAF was facing.
>I think that the parameters may well have changed with the introduction of the gyro gunsight in 1944.
In my opinion, the value of the gyro gunsight often is a bit overestimated. It requries a steady tracking shot with a full second spent by both the target and the shooter in a stabilized flight situation, and commits the attacker to a pursuit curve. Experienced pilots actually disliked the gyro gunsights, preferring a fixed sight and collision course attacks, because you can press these to a closer range (making the range problem easier) and at the same time avoid committing yourself to a turnfight. Besides, it allows greater angles-off, which increases the damage if you hit.
The Luftwaffe in particular avoided pursuit curve attacks on bombers because that while that made the firing solution for the attacker easier, the firing solution for the bombers' gunners became much easier, too :-)
Regards,
Henning (HoHun)
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Hi Henning,
If you turn to page 94 of your copy of 'Flying Guns: World War 2' you will see an official British diagram of the benefits of a larger dispersion in deflection shooting. In the case of an attack at 7 degree angle against a 250 mph target at 250 yards, it shows that if the pilot aims straight at the target (i.e. no lead) a 0.3 degree dispersion would result in a miss while a 1 degree dispersion would result in hits.
I agree with you that the most skilled pilots probably gained no benefit from gyro sights. But these represented only a small percentage of the pilots. When USAAF officers observed tests of the GGS they reckoned it would double the chance of an average pilot scoring hits.
Tony Williams: Military gun and ammunition website (http://www.quarry.nildram.co.uk) and Discussion forum (http://forums.delphiforums.com/autogun/messages/)
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Hi Tony,
>If you turn to page 94 of your copy of 'Flying Guns: World War 2' you will see an official British diagram of the benefits of a larger dispersion in deflection shooting.
Sounds like a book I ought to have, but the price tag deterred me :-/
>In the case of an attack at 7 degree angle against a 250 mph target at 250 yards, it shows that if the pilot aims straight at the target (i.e. no lead) a 0.3 degree dispersion would result in a miss while a 1 degree dispersion would result in hits.
Beggars' hits, I'd call them ... I've just calculated that in the outer ring between the 75% and the 100% dispersion, you have only 25% of the hits, but 75% of the pattern area. That's just 9% of the firepower you have in the central area. (And in fact, near the outer rim it's even less than 9%.)
You're better off walking the fire of a low-dispersion gun over the target by NOT trying to track, but pulling through. That way you get the same spread vertically, but much better accuracy horizontally.
And 7° deflection, wow :-) That's almost a straight six shot.
But I've to admit that while at first, I thought not pulling any lead at all sounded a bit contrived, I now consider the setup as simulating a higher-deflection shot with some, but not enough deflection - so it might be a valid example anyway.
>I agree with you that the most skilled pilots probably gained no benefit from gyro sights. But these represented only a small percentage of the pilots. When USAAF officers observed tests of the GGS they reckoned it would double the chance of an average pilot scoring hits.
Oh well, from all I know, they might just have pulled a nice round number out of their hat.
(And note that getting hits is not the same as getting kills ... for a kill, you need to hit decisively.)
Regards,
Henning (HoHun)
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Some quotes from 'Flying Guns - World War 2: Development of Aircraft Guns, Ammunition and Installations 1933-45':
"German research in the early 1940s indicated that most successful attacks took place at zero deflection and the maximum angle of attack for effective shooting without a gyro sight was 15º. Many successful fighter pilots preferred to open fire at point-blank range in order to avoid the deflection problem altogether."
and:
"Gyro sights were first developed in the UK in the late 1930s, after combat tests using camera guns revealed the difficulties in estimating the amount of lead. The first model was tested in combat in 1941 in both fighters and bombers, but had many problems which were not resolved until 1943, when the sights were perfected as the GGS (gyro gunsight) Mk IIC (for turrets) and Mk IID (for fighters). These went into quantity production early in 1944 and, after demonstrations revealed the dramatic improvement in average shooting accuracy which resulted from their use, the USA adopted the sight as the Mk 18 (USN) and K-14 (USAAF). There can be little doubt that these sights contributed significantly to the excellent kill ratios achieved by Allied fighter pilots in the last year of the War."
Tony Williams: Military gun and ammunition website (http://www.quarry.nildram.co.uk) and Discussion forum (http://forums.delphiforums.com/autogun/messages/)
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"There can be little doubt that these sights contributed significantly to the excellent kill ratios achieved by Allied fighter pilots in the last year of the War."
IMO there surely were other factors, too, which could have affected such results: Huge advantage in numbers, tactical advantage in height over combat area, bad quality of opposing force, to name few.
I'd imagine a lead computing sight to be most effective when accurate range can be calculated -and that would need a radar.
Otherwise it depends very much of the visual intepretation of the sight circle size relation to target.
-C+
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Originally posted by HoHun
However, once you ask "How many pellets actually hit?", you'll see that if, for example, the shotgun cone is three times as large as the target, you're hitting only with an average of 11% of your pellets if your random aiming error is smaller than the dispersion.
Well, here HoHun understands whole idea of the dispersion wrong.
Let's assume that we need say 10 hits to destroy the target. With the large dispersion shotgun we get say in average 10 hits in every case but with the small dispersion shotgun we need to shoot in average ten times to actually hit target but in that case we get in average 1000 hits. Which of these shotguns is more effective?
Besides aiming error is most likely systematic; too little lead.
gripen
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So how many rounds do you have to actually shoot to get those hits with a high dispersion gun?
-C+
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Hi Tony,
>"German research in the early 1940s indicated that most successful attacks took place at zero deflection and the maximum angle of attack for effective shooting without a gyro sight was 15º. Many successful fighter pilots preferred to open fire at point-blank range in order to avoid the deflection problem altogether."
That's a good description :-) However, the last two sentences implicitely describe two extremes of a fluid relationship - long range, low deflection capability, and extremely short range with high deflection capability. At intermediate ranges, the possible deflection was something in between.
I'd say the point-blank range comment indicates that you agree on the value of short-range high-deflection attacks (I call them collision-course attacks)?
>"Gyro sights were first developed in the UK in the late 1930s, after combat tests using camera guns revealed the difficulties in estimating the amount of lead. The first model was tested in combat in 1941 in both fighters and bombers ...
The UK was certainly leading the field in defensive armament. I think the gyro sights were more valuable for bombers than for fighters, however - but of course I don't deny they were great for fighters, too. It's just think that the enthusiasm shown by some authors is a bit exaggerated. They were a useful tool, but not without limitations - for example, they required an accurate range estimation, and the ranging mechanism was quite similar to that of the British fixed gunsights. As you've pointed out, the RAF pilots had considerable ranging difficulties with those.
>There can be little doubt that these sights contributed significantly to the excellent kill ratios achieved by Allied fighter pilots in the last year of the War."
Hm, the Luftwaffe achieved excellent kill ratios against the Soviets, too, but without gyro gunsights. I'd be hesitant to attribute a general phenomenon to a single factor.
Regards,
Henning (HoHun)
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Originally posted by Charge
So how many rounds do you have to actually shoot to get those hits with a high dispersion gun?
I don't know if this is about my two shotgun example. Assume that the dispersion of the high dispersion shotgun is larger than aiming error so some amount of salt projectiles (say at least ten) will hit in every case.
Basicly if the dispersion does not give any advantage, they would have been shooting birds with the rifles. Shooting large amount of projectiles (burst) without dispersion is basicly same thing as shooting a single round.
gripen
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Hi Charge,
>So how many rounds do you have to actually shoot to get those hits with a high dispersion gun?
I'll try to explain with a somewhat simplified example:
Assume a 12.7 mm MG that needs 60 hits on a target to bring it down. You have two versions of it, one with 2 mil dispersion and one with 4 mil dispersion radius.
Assume that pilot-induced aiming error increases total dispersion to 5 mil and 7 mil radius respectively.
Assume a target area of 1.54 m^2.
At 100 m, the target is completely within both dispersion radii. You get 100% hits with both weapons, so you need to fire 50 rounds.
At 200 m, the target fits perfectly into the the 75% dispersion radius of th large-dispersion weapon. You need to fire 80 rounds for a kill now.
The target also fits perfectly into the the 100% dispersion radius of the low-dispersion weapon. You still need to fire only 50 rounds for a kill here.
At 400 m, the target is caught firmly in the 75% dispersion circle of the large-dispersion weapon, filling only one quarter of it. That means only 18.75% of the rounds hit, or 320 have to be fired for a kill.
With the low-dispersion weapon, the target is caught just as firmly in the 75% dispersion circle, but fills 50% of it. That means you get the kill with just 160 rounds.
The idea that high dispersion improves kill chances is in error. It can only be justified by declaring that the pilot knows the correct aiming point and subconsciously avoids it.
The RAF initially used very long harmonization ranges, which gave them a large dispersion at normal (short) combat ranges. They were having all the aiming difficulties Tony described, and yet they quickly discovered that the way to get kills was to change harmonization to short ranges in order to keep dispersion to a minimum.
Whatever experiments were tried later, the RAF battle experience was "use the tightest possible pattern".
Regards,
Henning (HoHun)
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"The idea that high dispersion improves kill chances is in error. It can only be justified by declaring that the pilot knows the correct aiming point and subconsciously avoids it. "
Gripen, the amount of rounds to achieve those hits is not irrelevant as the a/c cannot carry infinite amount of mg rounds.
So the choise of weapon dictates also how it has to be used in aircombat.
The 303s the Brits used in BoB had a high probability of pucturing a radiator or a fuel or oil line but they were hardly able to inflict critical damage without firing at an extremely close range. But that was enough in that strategic situation. Many a/c ditched into channel or fell in Britain.
Imagine same kind of weapons in German a/c. The losses for RAF would have been smaller as the lack of critical damage would have left the RAF a/c a high probability of surviving the encounter because they always would have been able to ditch near some of their own fields. So the LW had to have heavy armament to achieve even what they did.
***
"The idea that high dispersion improves kill chances is in error. It can only be justified by declaring that the pilot knows the correct aiming point and subconsciously avoids it. "
HoHun, the projectiles in high dispersion do not avoid the area in the middle of the hit pattern but spread randomly over it with the preference being in the center providing that the weapon is in a fixed mounting.
Firing a high dispersion gun at long ranges is obviously a waste of time but at certain ranges it has an advantage of the dispersion providing that the projectile has ability (at that range) to inflict damage where ever it may hit the enemy a/c. That is unfortunately not the case as the bad dispersion is usually related to a light projectile and high ROF. But if you hit the pilot, or a coolant, oil, or fuel line or radiator that is usually enough, depending on if the damaged a/c can handily RTB which was not the case for German a/c for example during BoB.
So what I am trying to say is that the effectiveness of a high or low dispersion gun depends on the strategic and tactical situation it is used in. Obviously during the last stages of WW2 the experience had shown that the increase in speeds and amount of defensive armament in bombers required lots of damage in shortest time possible -thus the cannon armament became a necessity.
I'd take a dangerous step here and claim that if the situation had gone to worse direction for the allies the US, too, would have had to introduce the cannons into aircraft participating in aerial battle. For ground strafing the 50Cal was surely better. But that probably belongs to another thread.
Sorry, I went quite far from the original subject.
-C+
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Hi Charge,
>HoHun, the projectiles in high dispersion do not avoid the area in the middle of the hit pattern but spread randomly over it with the preference being in the center [...]
Correct. And the same is true for pilot aiming errors. To reap any benefit from a large-dispersion weapon - which concentrates its fire on the aim point, just like a low-dispersion weapon -, the pilot would have to involuntarily avoid the correct aiming point.
Only then the large-dispersion weapon's higher hit concentration out of the centre of the pattern would improve kill chances.
If the pilot's aim is not avoiding the correct aiming point, but merely inaccurate, the low-dispersion weapon's higher concentration of fire in the centre of the pattern makes it more lethal even if the aim is subject to errors.
>But if you hit the pilot, or a coolant, oil, or fuel line or radiator that is usually enough, depending on if the damaged a/c can handily RTB which was not the case for German a/c for example during BoB.
True :-)
>Obviously during the last stages of WW2 the experience had shown that the increase in speeds and amount of defensive armament in bombers required lots of damage in shortest time possible -thus the cannon armament became a necessity.
Well, the Luftwaffe actually had developed cannon from the mid-1930s on, and intended them as general anti-aircraft weapon, so I think your sentence could be misunderstood. If your main point is that the Luftwaffe would have been off worse in 1944 with machine guns instead of cannon, I certainly agree.
>I'd take a dangerous step here and claim that if the situation had gone to worse direction for the allies the US, too, would have had to introduce the cannons into aircraft participating in aerial battle.
Again, I agree. Using the 12.7 mm machine guns for air-to-air combat was a bit of a dangerous luxury - the RAF had actually been in a bad situation in 1940, which might explain their different weapon selection.
>Sorry, I went quite far from the original subject.
Well, you highlighted a new aspect of a much discussed topic, so it was an interesting digression :-)
Regards,
Henning (HoHun)
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A couple of points may be worth emphasising:
High dispersion only works if each individual hit is capable of inflicting significant damage. The RAF were forced to adopt a closer concentration of the .303 guns in the BoB (much against their will) because the damage inflicted by an individual bullet was usually small, so they had to concentrate a large number of hits in a small area to have much effect.
The aiming of most pilots in deflection shooting was CONSISTENTLY poor, in that they usually seriously underestimated the lead required. With a precisely accurate gun they would therefore have missed virtually every time. A dispersed set-up improved their chances of scoring SOME hits.
Tony Williams: Military gun and ammunition website (http://www.quarry.nildram.co.uk) and discussion
forum (http://forums.delphiforums.com/autogun/messages/)
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I was on a site checking out some things for CFS3 and found this. I thought that it might help you out. Here is the link.
http://www.avhistory.org/
Go to Knowledge base drop down and then to "1% Standards" --> WW2 gun parameters.
Might be some info that can really help you out.
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Hi Tony,
>High dispersion only works if each individual hit is capable of inflicting significant damage.
I see your point, but my point is that even then, low dispersion works better :-)
>The aiming of most pilots in deflection shooting was CONSISTENTLY poor, in that they usually seriously underestimated the lead required. With a precisely accurate gun they would therefore have missed virtually every time.
Well, air combat is highly dynamic. It's not like an artillery duel where you set up the guns in fixed positions and then slug it out.
In air combat, the aircraft move in 3D, and it's rare that you get into a position where the target is static in the sights of the attacker for any length of time. As long as we're talking about manoeuvring tarets, that usually happens only if the defender is surprised or if he is attempting to run away in a straight line.
The amount of "static" dispersion is not a help in these situations since the attacker usually has the time to set up an accurate shot with a low aiming dispersion there, so a low-dispersion weapon means he can score more hits.
Number two of "Sailor" Malan's "Ten Rules" was: "Whilst shooting, think of nothing else, brace the whole of your body, have both hands on the stick, concentrate on your ring sight." Obviously, relaxing a bit would increase uncontrolled dispersion, which you'd usually want to avoid.
In a manoeuvring fight, "static" dispersion is not that important either because it's two-dimensional. It's easy for the pilot to create "dynamic" dispersion by handling of the stick and rudder if he needs it, and he can actually create one-dimensional dispersion by "hosing" the target along a certain axis.
For example, it's usually pretty easy to align the sight with the direction of flight of a crossing target. Estimating the correct lead is much more difficult. Firing a long burst on a collision-course attack without turning the aircraft will create a pattern that extends in time rather than in space (funny way to look at it, but still :-), and because the target has to fly through the pattern, it will probably get hit.
A more conventional example would be the target that's attacked with a tracking shot. Using "static" dispersion in a stationary situation, you'd hold your aircraft in a steady turn matching the target's. The pattern will not only extend fore and aft of your aiming point, which is useful if you don't know the correct amount of lead, but also left and right, which is not that useful since the aircraft fuselage is pretty narrow. (The wings are hard to hit as due to their shorter depth, they require even more accurate lead to hit.)
Using "dynamic" dispersion, you'd usually pull too much lead, start firing, and relax the stick while holding the trigger. That will create a pattern that extends just as far fore and aft as with the high-dispersion weapon, or even wider if you desire, but still is so narrow that you can align most of it with the fuselage which is the best target anyway.
For example, you might get a 3 m diamter "static" dispersion circle with a large-dispersion weapon. You'd cover the same 7 m^2 area with a low-dispersion weapon with a 1.5 m by 4.7 m "dynamic" disperion pattern, with the 4.7 m extension along the axis of the lead, increasing your hit chances by about 50% if your main aiming error is caused by the mis-estimation of the necessary lead.
It's much easier to do then to explain :-) In fighter pilot slang, you might describe it as "hosing down" the target, if you're familiar with that term.
Regards,
Henning (HoHun)
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Hi Henning,
I think what you are forgetting is that most fighter pilots in WW2 had very little (if anything) in the way of realistic firing practice before entering combat, gained little useful practical experience in combat shooting, and were usually in a blind panic then anyway. The most that could be expected of them was to point the sights at the target and fire. Only a very small minority had the skill and coolness to achieve success with any kind of deflection shooting - which is why something like 90% of all kills were achieved by 10% of the pilots.
Perhaps one of the pernicious effects of modern combat sims - where people can practice for hours in a stress-free environment - is that they make people devalue just how very difficult it was for the vast majority of WW2 pilots to shoot anything down. For the few experts a wide dispersion would be a nuisance because it would reduce the lethality of their fire. But for the vast majority, the 'shotgun' effect of a wide dispersion gave them a better chance of scoring hits. There is a very good reason why people don't go hunting birds on the wing with rifles - or even machine guns!
Tony Williams: Military gun and ammunition website (http://www.quarry.nildram.co.uk) and discussion
forum (http://forums.delphiforums.com/autogun/messages/)
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Hi Tony,
>I think what you are forgetting is that most fighter pilots in WW2 had very little (if anything) in the way of realistic firing practice before entering combat, gained little useful practical experience in combat shooting, and were usually in a blind panic then anyway. The most that could be expected of them was to point the sights at the target and fire.
Well, my point is that even then, dispersion harmed more than it helped.
With mistakes of that magnitude, about the only way to bring down someone is a straight six shot without any deflection at all.
However, in that situation, more dispersion just means fewer hits as all errors involved are of random nature.
The trembling hands of a panicked pilot would be enough to increase dispersion beyond what an ace might experience. However, this was a problem, not a solution.
>Perhaps one of the pernicious effects of modern combat sims - where people can practice for hours in a stress-free environment - is that they make people devalue just how very difficult it was for the vast majority of WW2 pilots to shoot anything down.
True :-) Deflection shooting can be mastered completely given enough practice. It's something the human brain was set up to do during millions of years of evolution.
>There is a very good reason why people don't go hunting birds on the wing with rifles - or even machine guns!
Well ... this reason is that shotguns have a very rapid rate of fire, firing hundreds of projectiles in an instant. If you'd slow that shotgun down to the rate of fire of the weapons you're comparing it to, it's quite doubtful that you'd still be happy about its high dispersion.
And shotguns have a terrible overkill capability, too - they kill with one shot, even if the vast majority of the projectiles misses. If birds were a lot thougher than they actually are, the shotgun would lose a lot of its appeal.
Because the difference between a shotgun and a machine gun is much bigger than it appears at first, the shotgun example really isn't that helpful.
Regards,
Henning (HoHun)
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All I can say, Henning, is that during WW2 the RAF disagreed with you - their studies with the Hispano showed that some dispersion of fire would increase the hit probability.
Tony Williams: Military gun and ammunition website (http://www.quarry.nildram.co.uk) and Discussion forum (http://forums.delphiforums.com/autogun/messages/)
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Originally posted by Tony Williams
some dispersion of fire would increase the hit probability.
At the same time it will decrease the chances of concentrating the fire on one spot.
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Hi Tony,
>All I can say, Henning, is that during WW2 the RAF disagreed with you - their studies with the Hispano showed that some dispersion of fire would increase the hit probability.
Well, that statement doesn't qualify the exact conditions, so it's not very useful. It certainly seems to be overly pessimistic about the pilots' deflection shooting abilities.
The Luftwaffe used the low-dispersion, low-velocity MG FF/M with good effect, and I'm not aware of any complaints about this battery. By the RAF approach, you'd have thought that the low velocity should make deflection shooting even more impossible than with RAF guns, and the low dispersion prevented any stray hits on a target that's far away from the pilot's faulty aiming point.
To me, this sounds a lot like the RAF had exceptionally poor standards in aerial gunnery training, as other air forces besides the Luftwaffe had good confidence in the effectiveness of aimed fire, too. The US Navy thrived on deflection shooting, using it as one of their means of breaking the Zero's superiority in the Pacific. I seem to remember reading that the Polish squadrons in the RAF outperformed their hosts in gunnery accuracy, too, which would be an indication of a training deficiency on part of the RAF.
(Just to make sure - the Mölders/Galland debate was about firepower, not about accuracy. The MG151/20 in an engine mount had just the same low dispersion as the wing-mounted MG FF/M. And fuselage-mounting, which yielded low dispersion figures, was considered "ballistically ideal" by the Luftwaffe.)
Regards,
Henning (HoHun)
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I believe you are right that RAF gunnery training was poor - it was that realisation which led to the introduction of the gyro gunsight, as I've said. However, I don't know that the training of other air forces was much better. Don't forget the German analysis that most successful attacks were at zero deflection, with 15 degrees being the maximum. I believe that the USA made a major effort to improve the realism of their training during the course of the war, but they still eagerly seized on the gyro gunsight.
When you think about it, realistic training in deflection shooting was actually very difficult until the advent of combat simulators. They could show pictures of deflection shots to indicate the aiming marks, but there were so many variables that that could only have given a general idea. Pilots could practice attacks using camera guns but there would be a long delay before the film could be analysed and used to help indicate problems and this would also be very resource-intensive, so I suspect that this wasn't used that much. It tended to be country boys with much shotgunning experience who did best.
TW
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Hi Tony,
>However, I don't know that the training of other air forces was much better.
At least the Luftwaffe und the US Navy devoted special attention to deflection shooting in their training.
Remember that the Luftwaffe went into the Battle of Britain with low-velocity, low-dispersion cannon - if their gunnery standards would have been as bad as you seem to believe the RAF's were, they would have found gunnery a lot more difficult than the RAF with their high-velocity, high-rate of fire, high-dispersion MGs.
However, I'm not aware of the Luftwaffe considering their gunnery performance lacking in any way. Even Galland, who voted for more guns on the Friedrich to make it easier for the average pilot to knock down enemy aircraft, intended to keep the low-velocity, low-dispersion MG FF/M cannon.
If deflection shooting was that dficult, and if dispersion was that important, things would have gone different in the Luftwaffe.
>Don't forget the German analysis that most successful attacks were at zero deflection, with 15 degrees being the maximum.
Well, without the details of that study, I'm afraid that doesn't allow any conclusion. Those zero deflection attacks are usually the result of the target failing to notice the attacker, and quite naturally, these are most successful by far.
>I believe that the USA made a major effort to improve the realism of their training during the course of the war, but they still eagerly seized on the gyro gunsight.
No doubt, the LCOS was a good thing. It's just that it's impossible to make assumptions about gunnery standards based on the fact of its introduction.
Regards,
Henning (HoHun)
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Well, as noted above, the LW found out from gun camera analyses that an average LW pilot got just 2% hits when shooting on heavy bomber size target. The range is not specified but apparently this means all ranges, so 2% might be for something around 200 m, this means that at 500 m there would have been much less hits.
gripen
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Hi Tony,
>However, I don't know that the training of other air forces was much better. Don't forget the German analysis that most successful attacks were at zero deflection, with 15 degrees being the maximum.
This link to the Luftwaffe training booklet was already posted on another thread, but you might have missed it:
http://rafiger.de/Homepage/Pages/Schiessfibel.html
Page 14 re-inforces I point I've made in this thread: Dispersion doesn't help you. The Schießfibel:
"Accordingly [referring to example illustrations for faulty deflection shooting], don't rely on weapon dispersion - it won't help you if your aim is flawed! You can see here clearly how ACCURATELY you have to know and to apply deflection, or your fire will miss. But if you think now that you could simply adjust your MGs for a larger pattern to hit more reliably, then you're making a mistake. Your experience will be similar to that of the wild hunter in the picture on the right."
The latter advice is repeated on page 28:
"Another thing: Please don't invent new harmonization patterns, for example by adjusting the trajectory cross-over 100 m out etc. The ordered harmonization has been carefully devised by combat veterans and is good."
>It tended to be country boys with much shotgunning experience who did best.
Interestingly, Priller's book on the JG26 gives a breakdown of professions among the fighter pilots who served with JG26 and scored victories with JG26 or other units:
No/unknown pre-service profession: 126 pilots, 261 victories (average 2.1)
Career soldiers: 152 pilots, 1752 victories (average 11.5)
Pilots with pre-service profession: 166 pilots, 989 victories (average 6.0).
A detailed breakdown of the high scorers is available for III/JG26:
1 student (55 victories)
1 public servant (40)
2 merchants (64/27)
1 employee in public service (173)
2 technicians (71 each :-)
2 mechanics (24 each)
3 mechanics/precision instrument makers (63/52/40)
1 baker (48)
1 furrier (27)
1 optician (22)
1 carpenter (190)
1 musician (58)
1 metal worker/craftsman (89)
1 farm hand (20)
I assure you that it was Priller himself who put the single farm boy at the end of the list! :-) It was actually Erich Scheyda (who stated his profession as "coachman"), 188 combat sorties, 20 victories (32 points), KIA 25 years old.
Of the 166 pilots with a pre-service profession, craftsmen were the largets group with 90 pilots, the largest group of them being mechanics/fitters (25). It appears that a fair proportion of the latter were former ground crewmen who volunteered for pilot training.
If anything is striking about the list, it's - ironically! - the absence of farm boys. I think this might be systematic as men with agricultural professions might have been exempted from the draft to a certain degree in order to secure Germany's food supply. (Germany hadn't forgotten the food shortages in WW1, and Hitler really feared a revolution like it occurred at the end of WW1.) A contributing factor might be that a good education helps you to become a successful pilot, and farm boys might have been a disadvantage there.
Another irony about this topic is that due to the German laws gouverning hunting, it had become much more difficult for "ordinary" people to participate in hunting activities. It's ironic because this was a direct result of Hermann Göring's own hunting passion, and by devising the laws to keep hunting elitary, he was actually sabotaging the gunnery training of potential fighter pilot aspirants :-)
Among Göring's many titles was that of "Reichsjägermeister", and for once "Jäger" meant "hunter" literally instead of the "fighter pilot" we've gotten used to :-)
Regards,
Henning (HoHun)
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The public service employee and carpenter scored 173 and 190 resp.?
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Hi Moot,
>The public service employee and carpenter scored 173 and 190 resp.?
"Behördenangestellter" resp. "Schreiner", with 173 resp. 190 victories according to "J.G. 26 - Geschichte eines Jagdgeschwaders" by Josef Priller.
Regards,
Henning (HoHun)
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Hi Tony,
>If anything is striking about the list, it's - ironically! - the absence of farm boys. I think this might be systematic as men with agricultural professions might have been exempted from the draft to a certain degree in order to secure Germany's food supply.
I just asked a friend about this who is a bit of a specialist for the period, and he confirmed that men who had a job connected with agriculture were usually categorized "uk" by the Nazis, meaning "unabkömmlich" - "indispensable", so they were not allowed to be drafted.
The further the war progressed, the more treasured an "uk" classification became. When the military pressure increased, many "uk" classifications were revoked, of course ...
Regards,
Henning (HoHun)