Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: Urchin on April 25, 2002, 12:03:03 PM
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What are the differences between the Type 99 cannon mounted on the A6M-5 (and the N1K2) and the Oerlikon MG-FF mounted on the 109E4? I thought the Type 99 was a direct copy (manufactured under license) of the Oerlikon design, but this doesn't seem to be the case in Aces High.
The A6M5's cannons have a straighter trajectory, higher velocity, and they hit harder than the 109E4's cannons do. Why?
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The Type 99-1 was the rough equivalnt to the MG-FF
However, the 99-1 was replaced with the 99-2. The type 99 Model 2 fire the rounds at a greater velocity, but actually had a slower rate of fire than the Type 99 Model 1.
Here are some common usages in IJN fighters.
A6M2 - Type 99 Model 1
A6M3 32 - Type 99 Model 1
A6M3 22a - Type 99 Model 2
A6M5 - Type 99 Model 2
J2M3 - Type 99 Model 1 and Type 99 Model 2
N1K2-J - Type 99 Model 2
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Type 99-2: 129 g, 490 rpm, 625 m/s
MG-FF: 134 g, 520 rpm, 600 m/s
..and for comparison...
Hispano Mk.II: 130 g, 600 rpm, 880 m/s (But... it weighs almost twice what the MG-FF does)
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Ok, I'd like this explained/clarified for me.
The MG-FF fires a heavier bullet (it is 5 grams heavier, right?), at a slightly lower speed (25 m/s less, right?). So, as far as hitting power goes, how do you calculate it? Is it weight times muzzle velocity?
If it is weight times muzzle velocity, the MG-FF comes out at 80,400 somethings lol.
The Type 99 Mk2 comes out at 80,625.
The Hispano comes out at 114,400.
Well, it appears to be obvious that the Hispano (I keep having to fight typing Hizooka) should hit harder than the MG-FF and the Type 99 Mk2, and it does in AH.
However, the results between the Type 99 Mk2 and the MG-FF are really, really close. As it is now, a MG-FF round probably falls about halfway between a .50 caliber round and a MG151 round.
The Type 99 seems to hit about as hard as the Mg151 does.
Add to that a trajectory that seems somewhat worse than the 30mm Mk108 and you have a weapon that is essentially useless, in my opinion.
Just from laymens experience in the game, I'll try to list the damage (against other planes) for the guns I've got experience with.
37mm (Yak gun): 1-2 hits will kill.
30mm Mk108: 1-2 hits will kill.
23mm (Il-2 gun): 2-4 hits will kill (2 on the same spot will usually kill)*
20mm Hispano: 2-4 hits will kill (see above)*
Mg151/20: 3-6 hits will kill (usually 3-4 in the same spot will kill)
Type 99: 3-6 hits will kill (see above)
MG-FF: 8-12 hits will kill (I've hit someone 6-7 times in the same spot for no damage several times, at ranges from 300 to 100 yards)
.50 caliber M2: 15-20 hits will kill (sometimes more, up to 30 or so).
Mg 131: 15-25 hits will kill (less if you are close, more if you are far away
C202 12.7mm: 20-25 hits, usually.
7.92 LW guns: See above
.303s : See above
Effective range: Tail shot/ Head on shot - Range you can fire and expect to land a burst.
.50 caliber: 800 yards/ 1200 yards (thats conservative)
20mm Hispano: 600/ 1000 (or so) yards.
Mg131: 600/1000 (or so) yards.
Mg151/20: 400/800 (or so) yards.
Type99: 400/800 (or so) (Honestly seem a lot like 151/20s to me)
C202: see above
7.92 LW: 400/800 (or so)
.303 - honestly not much experience, I'd guess 400/800ish.
MG-FF: 150/450 or so.
And finally, trajectories.
.50 caliber: nice and flat almost out to 1000 yards.
20mm Hispano: nice and flat to about 800 yards or so
Mg131: Nice and flat for about 600-700 yards.
Mg151/20: Nice and flat for about 400 yards.
Type99: See above.
.303/7.92: Flat for about 400-500 yards.
Mk108: flat for about 200 yards.
MG-FF: flat for maybe 150 yards.. maybe.
Of course, this is all just what I've experienced in Aces High. I'm not a ballistics expert, never fired any of these guns in real life. I'm perfectly happy with the MG151/20, I've reconciled myself to the fact that it is no Hispano. What I don't understand is why the MG-FF is so horrible? Why does it have so much drop in such a short period of time? Furthermore, if you are trying to take a tracking shot on someone in a flat turn (assuming you are behind them) you have to lead the other plane so much (even at 100 yards) that you can't even SEE the other plane- it is somewhere around your instrument panel. You don't even have to lead that much with the Type 99s or Mg151s (what the particulars on the MG151/20 anyway?).
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The MG/FF has a metric calibre of 20 x 80RB. The muzzle velocity is 600 meters per second.
The Type 99 I has a metric calibre of 20 x 72RB. The muzzle velocity is 550-600 meters per second.
The Type 99 II has a metric calibre of 20 x 101RB. The muzzle velocity is 750 meters per second.
Essentially the Type 99 I is the same gun as the MG/FF on the Bf109E-4. They have nearly identical ballistics and are both limited to 60 rounds due to their drum feed mechanism. Both the MG/FF and Type 99 I are heavily based on the Oerlikon FF.
The Type 99 II was based on the Oerlikon FFL, which also allows the A6M5 and N1K2 to have much greater ammo supplies due to its belt feed mechanism.
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I don't understand, Karnak.
Whats the difference between a 20x80RB (whats an RB?) and 20x101RB?
Is the 20X101 longer?
Thanks for the info on the muzzle velocity though, that would explain why you dont have to lead as much with the Zeke as you do with the Emil.
Whats the stats on the MG151/20?
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Urchin you are forgeting I think this, The Japanese fired an almost all HEI ammo load they did not mix their chaines like the Germans did, I have been told the Type 99 rounds hit like 99% as hard as Hispano rounds due to the fact that the added chemical engery in these rounds is factored into their effectiveness in AH. In fact the AP round in the chain was the tracer so like only one in 4 or 5 was the AP rond all the rest were HEI.
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Urchin,
Quite honestly, I'm taking numbers straight out of Tony William's book. I don't know what all of the stuff means, "RB" for example. I was posting the data in the hope/assumption that it would be understood by people who know their ammo/guns. I do aircraft, not guns. ;)
Yes, the Type 99 II is longer than the Type 99 I or MG/FF. The length in this case is, I am pretty certain, including the cartridge. The weight of the shell given in Tony's book is the same for the Type 99 I and Type 99 II. I belive that the larger cartridge gives the Type 99 II its superior muzzle velocity.
Guns/cannon of interest as described by Mr. Williams:
Format: Gun(s) | Metric Calibre | Projectile Type/Weight gm | Muzzle Velocity m/sec | Muzzle Energy joules |
Breda-Safat 12.7mm, Ho-103: | 12.7 x 81SR | 36.7 | 760 | 10,600 |
.50" Browning M2 | 12.7 x 99 | AP/46 | 880 | 17,800 |
MG131 | 13 x 64B | HET/34 | 750 | 9,600 |
Type 99 I | 20 x 72RB | HE/128 | 550-650 | 19,000-23,000 |
MG/FF | 20 x 80RB | HE/134 | 600 | 24,100 |
MG151/20 | 20 x 82 | HE/115 | 710 | 29,000 |
Ho-5 | 20 x 94 | HEI/79 | 730 | 21,000 |
ShVAK, B-20 | 20 x 99R | HE/97 | 860 | 35,900 |
Type 99 II | 20 x 101RB | HE/128 | 750 | 36,000 |
Hispano Mk II | 10 x 110 | HE/130 | 880 | 50,300 |
VYa | 23 x 152B | API/200 | 880 | 77,400 |
MK 108 | 30 x 90RB | HE/330 | 505 | 42,100 |
MK 103 | 30 x 184B | HE/447 | 800 | 143,000 |
NS-37 | 37 x 195 | AP/735 | 900 | 298,000 |
Vickers Class S, aircraft | 40 x 158R | AP/1,130 | 615 | 214,000 |
BK 5 | 50 x 419R | AP/2,060 | 835 | 718,000 |
Molins 6pdr | 57 x 441R | AP/3,170 | 790 | 989,000 |
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There is a history and "family tree" of the Oerlikons, Type 99s, MG-FFs, MK 108 etc on my website (see "Of Oerlikons and Other Things")
The MG-FF and the Type 99-1 were effectively the same in their performance (127-134g at around 600 m/s). However, the MG-FFM, introduced in May 1940 in the Bf 109E-4, was modified to accept the new "Minengeschoss" mine shells. These were thin-walled, high capacity shells (they contained around 20g HE compared with a maximum of 10-11g for other 20mm) and only weighed 92g, which enabled the muzzle velocity to be upped to around 700 m/s. Because they were light and had a blunt shape, they lost velocity very quickly and had a relatively short range.
The Type 99-2 had a longer cartridge case to house more propellant, which put the muzzle velocity up to 750 m/s, using the same 127-134g shells. These contained about the same HE as the Hispano (ie 10-11g max).
Relative hitting power is a difficult one to summarise, because it all depended on the circumstances. The M-Geschoss was highly effective when it detonated in a confined space because it relied on blast effect to generate pressure. The other shells formed larger fragments when they detonated, sending these flying through the structure. This might be more or less effective depending on where it hit.
Tony Williams
Author: "Rapid Fire: The development of automatic cannon, heavy machine
guns and their ammunition for armies, navies and air forces"
Details on my military gun and ammunition website:
http://www.quarry.nildram.co.uk
Military gun and ammunition discussion forum:
http://forums.delphiforums.com/autogun/messages/
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Originally posted by Urchin
Ok, I'd like this explained/clarified for me.
So, as far as hitting power goes, how do you calculate it? Is it weight times muzzle velocity?
For kinetic energy its force = mass x acceleration
Acceleration is velocity squared/2
so its weight times the square of velocity/2.
This of course takes no account of drag or explosive energy (of a cannon round)
Hence a % difference in velocity has a far greater effect on kinetic energy (range and impact) than the the same % difference in weight. (a 4% difference in velocity is a 8% difference in Energy where as a 5% difference in velocity is a 12.5% difference in Energy.......... a 5% differnce in weight is a 5% diference in Energy)
This affects range and residue impact energy.
As others have said trying to factor this into a lethality constant is very hard due to the different circumstances a cannon round may find its self in when it explodes. And off course the potential chemical energy in the charge and how it is transfered to actual kinetic energy........ thin wall shells rely on pure explosive force acting on the surrounds........... thicker wall shells operate more like a grenade to convert the potential chemical energy into the kinetic of the shell fragments.
To be truly effective a thin wall shell will be required to penetrate into a confined space (eg wing section) whilst a thick wall shell can also do damage in the larger cavities and even some without penetrating the AC structure. As you have to sacrifice chemical energy to achieve a thicker wall you are therefore seeking a compramise.
This would be decided by your typical choice of target.
It would be an interesting addition to enable players to choose typical shell types for their AC guns just as they can for their tank rounds now.
HTC will be forced to tread a middle line on this but we can imagine the complexity with which they are faced in terms of subsequent range and lethality modelling.
Tilt
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Originally posted by Tony Williams
Because they were light and had a blunt shape, they lost velocity very quickly and had a relatively short range.
Would you agree that their "lightness" has little to do with the loss of velocity..............?
A large but light feather with a kinetic energy of 10,000 joules has the same kinetic energy (force) as a smaller but heavier brick with a Kinetic energy of 10,000 joules.
Indeed given the brick is heavier but slower the affects due to gravity on trajectory are greater.
Drag however directly bleeds kinetic energy and so our feather lighter but having a greater surface area suffers a reduction in velocity.
Given that Muzzle velocity compensated for weight to produce the same kinetic energy then indeed the smaller/lighter round would enjoy greater range.(if the drag coefficient for both were the same)
Tilt
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Originally posted by Tilt
Given that Muzzle velocity compensated for weight to produce the same kinetic energy then indeed the smaller/lighter round would enjoy greater range.(if the drag coefficient for both were the same)
Tilt
But the drag coefficient is directly affected by the weight for a given calibre. There are two elements in calculating the drag coefficient; one is the aerodynamic shape of the projectile, the other is the sectional density, which is a ratio between calibre and weight. The M-Geschoss was the same shape as a conventional shell but much lighter, so both its SD and ballistic coefficient were considerably worse. That is why it lost velocity more quickly. In fact, it lost 60% of its velocity at 600m, compared with around 40% for the conventional shell.
Tony Williams
Author: "Rapid Fire: The development of automatic cannon, heavy machine
guns and their ammunition for armies, navies and air forces"
Details on my military gun and ammunition website:
http://www.quarry.nildram.co.uk
Military gun and ammunition discussion forum:
http://forums.delphiforums.com/autogun/messages/
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Originally posted by Tony Williams
, the other is the sectional density, which is a ratio between calibre and weight.
I cant see the physics behind that...... is it an imperical factor?
If two projectiles had the same muzzle velocity but one weighed less........... then its(the lighter) total kinetic energy is lower and it will loose velocity quicker.... even if drag is the same.
in other words for the same muzzle velocity the lighter projectile will always loose velocity faster. (it has a lower kinetic energy)
but for the same energy at the muzzle (mass x accel) I would assume that given equal drag (aerodynamic) they would both loose velocity equally except the heavier would be more subject to gravity.
This is begining to look a bit pedantic I just wanted folk to be wary of thinking that lighter always meant shorter range. When really its kinetic energy and drag(aerodynamic) that effect range.
Tilt
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Hi everyone,
I'd like to point out that the kinetic energy of a projectile isn't necessarily proportional to its hitting power. The German mine shells had a much greater explosive content than normal explosive rounds, and they were designed to wreck an aircraft's structure.
While armour piercing rounds had a much better penetration than mine shells, they had to rely on hitting critical components, which were few and small. As mine shells attacked the aircraft structure, they were effective almost regardless of where they struck the target.
Since the main destructive component of the mine shells was the explosive content, the MG FF/M mine shells were just as effective as the MG151/20 mine shells, though of course the latter's higher muzzle velocity made hitting easier.
Regards,
Henning (HoHun)
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Originally posted by Tilt
This is begining to look a bit pedantic I just wanted folk to be wary of thinking that lighter always meant shorter range. When really its kinetic energy and drag(aerodynamic) that effect range.
Tilt
To be precise it is the combination of ballistic coefficient and muzzle velocity which determine the range.
Ballistic coefficient is important because it determines the rate at which the projectile slows down (the "aerodynamic drag", if you like).
In conjunction with the muzzle velocity, the ballistic coefficient determines the projectile time of flight, which is the key figure for two reasons; the shorter the flight time, the greater the hit probability, and also the less time gravity has to work on the projectile, so the less it will drop below the line of sight.
For those reasons, the flight time determines the effective range, although if you are relying on kinetic energy the effectiveness of the bullet strike will obviously reduce with range, whereas as Henning pointed out, cannon shells relying on HE to do the damage stay more or less equally effective at all practical ranges.
Tony Williams
Author: "Rapid Fire: The development of automatic cannon, heavy machine guns and their ammunition for armies, navies and air forces"
Details on my military gun and ammunition website:
http://www.quarry.nildram.co.uk
Military gun and ammunition discussion forum:
http://forums.delphiforums.com/autogun/messages/
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Tony,
Are you working on any new books?
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Originally posted by Tony Williams
To be precise it is the combination of ballistic coefficient and muzzle velocity which determine the range.
Ballistic coefficient is important because it determines the rate at which the projectile slows down (the "aerodynamic drag", if you like).
I miss a refernce to a "ballistic coefficient" in "Rapid Fire"
I note an approach to the subject in p28 (momentum...which is also mass x speed) however I have been arguing to show that the muzzle energy is the better simplistic describer (as stated on p29) of range rather than weight and drag (which ignores the muzzle velocity).
I note that p16 explains that range was sacrificed by going to a lighter shell on a particular round type even tho muzzle velocity was increased however I assume that the net muzzle energy was also reduced when going to the lighter shell too?
eg What was the muzzle energy of the 20 x 82 HE compared to the (slower but heavier) 20 x 82 AP/HE (I only see figures for the HE)
of interest then from this discussion is a comparison of range for the 20 x 82 HE and the 20 x 99R HE. The 99R has lower drag and higher muzzle energy...........I would expect its flat trajectory to be significantly longer?
Would it be possible to add a section on the physics of ballistics (both propellent and explosive) and trajectories plus a comparaive assessment of various rounds ............in one of your future works?
Tilt
btw I fully concurr with both your and Hohuns comments on ballistic/ kinetic variances at target.
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Hi Tony,
German documents indicate that the MG151/20 mine shells were about 3.75 times as effective against four-engined bombers as the MG151/15 projectiles.
The kinetic energy the 15 mm projectiles carried was about 3.3 times that of the 20 mm shells for the same effect.
The 20 mm mine shells contained 18.7 g explosives, the 15 mm HEI shells 2.8 g each.
Do you happen to have a comparative value for the Hispano HEI shells?
Regards,
Henning (HoHun)
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I am, this weekend, finalising the next book for sending to my publisher, which is scheduled to be in the shops in March next year (no, don't ask me why it takes so long).
It is the first of a three-book series on the development of aircraft gun, ammunition and installations. My co-author is Emmanuel Gustin, who knows a lot more about aircraft and installations than I do. The first volume covers 1933-45, the next will be 1914-33 and the last 1945-2002. The first volume looks as if it's going to be twice as big as the others...
I have been spending a long time collecting as much info as I can concerning ammunition loadings, HE weights, composition and performance, plus AP performance, from a wide range of sources (thanks, Brady and Henning, among many others!). Some interesting comparative information came from British tests on German and British ammo during WW2.
The issues of sectional densities, ballistic coefficients and range are covered, and I have ballistic data on the German ammo in particular.
To answer the question, the Hispano shell held 10-11g of HEI.
Tony Williams
Author: "Rapid Fire: The development of automatic cannon, heavy machine guns and their ammunition for armies, navies and air forces"
Details on my military gun and ammunition website:
http://www.quarry.nildram.co.uk
Military gun and ammunition discussion forum:
http://forums.delphiforums.com/autogun/messages/
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TY sir:)
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Ok, one more question. Assuming you can hit with the MG-FF on the 109E4, each shell that hits should be roughly equal in damage to the Mg151/20? At least if I read that right.
In Aces High, it isn't even close. The single Mg151/20 in the nose of the 109F4 does WAY more damage than the wing-mounted MG-FF's in the 109E4. And it is easier to hit with to boot.
That would seem to indicate one of two things to me:
1. The MG-FF doesn't hit as hard as it should be hitting.
or
2. The MG151/20 is hitting harder than it should be hitting.
They aren't even close to the same hitting power. And no, I haven't run any scientific tests to 'prove' it, although they'd be fairly easy to run I think. I'm just making that claim on the basis of my experience in the various 109s, in Aces High (which admittedly isn't scientific in the least).
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The MG 151/20 should certainly be easier to hit with, for two reasons;
1. The projectile has a shorter flight time due to the higher MV.
2. The gun is centrally mounted, right under the sights, so there's no harmonisation problem.
There shouldn't be a significant difference in hitting power, although the API shells which were usually included in the belt mix would obviously have more kinetic energy.
Tony Williams
Author: "Rapid Fire: The development of automatic cannon, heavy machine guns and their ammunition for armies, navies and air forces"
Details on my military gun and ammunition website:
http://www.quarry.nildram.co.uk
Military gun and ammunition discussion forum:
http://forums.delphiforums.com/autogun/messages/
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So i would like to ask why hizookas are so effective in AH?
MG/FF M (109E, 190a5) 690m/s
MG151/20 790-805m/s
Mgeshoss 18.6g NP/HA40 (round 92g)
HS II 880m/s
HE/I 10-11g of ?TNT? (Also didn't they had problems with HE fuse - explosions outside fuselage, so AP/I was used instead)
AP/I 4.2g thermit, incendiary.
And yes, once again Mine round fired from MG/FF M and MG151/20 has equal hitting power. About 4 should be enough (75g of explosive) to destroy most single engined aircraft. (Note MK108 M-round 72g of explosive). Effect would much depend on construction of opposing aircraft.(Whether overpressure could build up easily or not, ie. wood skinned aircraft could usually absorb more hits than aluminum ones)
Ps.Sorry no mean to hijack this thread :D
hmmm...one thing im also interested about. How about effect of vibrations caused by airflow on wing mounted MGs/cannon? How much it causes dispersion?
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illo,
AH's damage model seems too simple to me to do adequate justice to the complexities of WWII aircraft armaments.
Consider that the AP round of a Hispano Mk II is most likely going to just make an entrance hole and an exit hole on a bomber due to the large amounts of bomber that aren't critical systems or structure, but rather just skin.
A Hispano Mk II AP round hitting a fighter, on the other hand, is much more likely to hit a critical system such as the engine, fuel, pilot or main spar (which it would break). I suspect that AP rounds would be just about as effective at killing fighters as the German Mine rounds. The German Mine rounds would, however, be much, much more effective at killing big aircraft like B-17s and Lancs.
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Nice little ammunition chart for you. (not for you tony, hohun. you already have one) :)
(http://www.kolumbus.fi/koponen.lauri/chart2.jpg)
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Karnak.
Yes, I agree. Ah models only heavy structural damage. (lost wings etc.)
With current DM AP rounds wouldn't have much to damage, while real fighters interior was full of more or less vital/vulnerable parts/systems.
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Originally posted by illo
So i would like to ask why hizookas are so effective in AH?
MG/FF M (109E, 190a5) 690m/s
MG151/20 790-805m/s
Mgeshoss 18.6g NP/HA40 (round 92g)
HS II 880m/s
HE/I 10-11g of ?TNT? (Also didn't they had problems with HE fuse - explosions outside fuselage, so AP/I was used instead)
AP/I 4.2g thermit, incendiary.
A couple of points.
First, M-Geschoss was never exclusively loaded in 20mm fighter gun belts; it was mixed with conventional HE-T (which only contained 3.7g HE) and API.
The Hispano HE was loaded with Pentolite (PETN+TNT) or Tetryl (US), the HEI had Tetryl (7g) and incendiary (4.3g).
The first version of the Hisso HE in RAF service had a superquick fuze which was ineffective, so until they developed a delay action fuze for the HEI they briefly reverted to a plain steel ball projectile as being more effective. The HEI was then mixed in the belt with SAPI, which contained 11g incendiary compound.
The question of aircraft damage has so many variables that it is difficult to generalise. When the RAF tested the German 20mm against the Hisso, they concluded that although the M-Geschoss was highly effective when it exploded in a confined space (eg a wing box), the Hisso would penetrate deeper and stood more chance of inflicting structural damage.
The M-Geschoss achieved its maximum effectiveness in 30mm calibre; the MK 108 was really designed around it, and fired nothing else.
Tony Williams
Author: "Rapid Fire: The development of automatic cannon, heavy machine guns and their ammunition for armies, navies and air forces"
Details on my military gun and ammunition website: http://www.quarry.nildram.co.uk
Military gun and ammunition discussion forum: http://forums.delphiforums.com/autogun/messages/
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Thanks tony. Much new information for me. Anything about when and which hispano ammunition type was generally used? (1940-45)
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Hi Karnak,
>I suspect that AP rounds would be just about as effective at killing fighters as the German Mine rounds.
While the fighter may have a larger proportion of vital components making it a better target for armour piercing rounds, it also features much smaller confined spaces which makes it much more vulnerable to mine shell hits, too.
German research indicated that a fighter's proportion of areas vulnerable to mine shells was even larger than a bomber's, and actually included almost the entire airframe.
I don't see any reason to assume that the relative effectiveness of mine shells versus armour piercing projectiles against fighters was any different than against bombers.
Regards,
Henning (HoHun)
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Originally posted by illo
Thanks tony. Much new information for me. Anything about when and which hispano ammunition type was generally used? (1940-45)
I believe that the changeover from HE through ball to HEI took place during 1941. Certainly by 1942 the RAF standard load was 50/50 HEI/SAPI, and it stayed that way thereafter.
Incidentally,the SAPI was a standard HE shell body with a hard steel cap instead of a fuze. The incendiary mix was ignited by the force of impact. It was capable of penetrating around 20mm armour - which was enough.
The RAF never used an AP shot, but the USAAF did adopt one (the M75). I don't know what use they made of it, though. The HE/HEI rounds for the USAAF were to the same spec as the RAF's, but I don't think they used SAPI.
Tony Williams
Author: "Rapid Fire: The development of automatic cannon, heavy machine
guns and their ammunition for armies, navies and air forces"
Details on my military gun and ammunition website:
http://www.quarry.nildram.co.uk
Military gun and ammunition discussion forum:
http://forums.delphiforums.com/autogun/messages/
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Hi Tony,
>When the RAF tested the German 20mm against the Hisso, they concluded that although the M-Geschoss was highly effective when it exploded in a confined space (eg a wing box), the Hisso would penetrate deeper and stood more chance of inflicting structural damage.
Removing the load-bearing skin of a stressed-skin airframe actually means structural damage :-)
I fact, the entire point of a mine shell is that it's unecessary to penetrate deeply or hit any special component to inflict strucural damage.
A fighter's fuselage was a valid target area for mine shells, too, by the way. The space confined within was small enough for mine shells to be effective.
Regards,
Henning (HoHun)
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True enough, Henning, although it did depend on the construction. The older types (especially fabric covered, like the Hurricane and Wellington) were relatively unaffected by blast damage. There were more subtle differences between different types of metal construction too, depending on the details of the structural design.
The main advantage in blowing off bomber wing sections seems to have been not so much that the target was immediately brought down, as that the aerodynamic penalty meant that the bomber was unlikely to make it back home. And of course, the fuel tanks were in the wings and fire was by far the greatest bomber-killer. This is why the Luftwaffe were showing a marked interest by the end of the war in HEI, with the emphasis on the I, in conjunction with hydrostatic fuzes.
Tony Williams
Author: "Rapid Fire: The development of automatic cannon, heavy machine
guns and their ammunition for armies, navies and air forces"
Details on my military gun and ammunition website:
http://www.quarry.nildram.co.uk
Military gun and ammunition discussion forum:
http://forums.delphiforums.com/autogun/messages/
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Originally posted by HoHun
Hi Tony,A fighter's fuselage was a valid target area for mine shells, too, by the way. The space confined within was small enough for mine shells to be effective.
Although comparing different calibres with different ROF........ the Russians seemed to find this as well when comparing the 20mm and 37mm Yak versions......... in terms of fighter kills per round.
As Tony's book shows the 37mm packed a much bigger explosive punch..........
Tilt
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Hi Tony,
>The older types (especially fabric covered, like the Hurricane and Wellington) were relatively unaffected by blast damage.
Sure, but except for the RAF, all major air forces could afford modern stressed-skin aircraft ;-)
>The main advantage in blowing off bomber wing sections seems to have been not so much that the target was immediately brought down, as that the aerodynamic penalty meant that the bomber was unlikely to make it back home.
Killing a target immediately is exactly what mine shells were made for.
The stressed skin is a soft target, but it's just as important for the structural integrity of an aircraft as the rigid wing spar. You don't need to pierce the heavy main spar - it's just as effective to tear off the light alloy skin. With a large hole, you don't even need to touch the spar - the wing will twist itself off under the aerodynamic loads. And while the main spar is hard to hit, and hard to damage, the skin is easy to hit and easy to damage.
Slow bomber deaths result from component damage from penetrating projectiles (or by collateral damage from mine shells). Quick bomber deaths result from structural failure, brought about by extensive destruction of the target's load-bearing aluminium skin.
Regards,
Henning (HoHun)
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HoHun,
It seems to me that you put to little stock in the ability of a round to penetrate into the aircraft. Blowing a hole in the fuselage skin is useful and does weaken the structure, but not nearly so as breaking the spar or punching a 20mm+ hole in the engine or pilot.
Tony,
I will definately be picking up you next book.
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Originally posted by Karnak
HoHun,
Tony,
I will definately be picking up you next book.
Glad to hear it. Please form an orderly queue :)
Tony Williams
Author: "Rapid Fire: The development of automatic cannon, heavy machine guns and their ammunition for armies, navies and air forces"
Details on my military gun and ammunition website:
http://www.quarry.nildram.co.uk
Military gun and ammunition discussion forum:
http://forums.delphiforums.com/autogun/messages/
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Hi Karnak,
>It seems to me that you put to little stock in the ability of a round to penetrate into the aircraft. Blowing a hole in the fuselage skin is useful and does weaken the structure, but not nearly so as breaking the spar or punching a 20mm+ hole in the engine or pilot.
I think I should clarify that I'm not talking about my personal opinion, but about German WW2 research here. Mine shell development was started because of the proven ineffectiveness of hole-punching. One has to punch that hole just in the right place, after all.
A typical WW2 fighter might present as little as 10% critically vulnerable surface - but with mine shells, as much as 90% of the target area can be hit effectively. That's a big lethality advantage for the mine shells, obviously.
But that's just for illustration - the Luftwaffe invented and perfected the mine shell, and they built most of their air-to-air weaponry program around it. Evidently, both research and combat experience had totally convinced them of the mine shell's effectiveness.
Not that there's no merit in punching holes - but the Luftwaffe was thinking in terms of weapons systems.
Regards,
Henning (HoHun)
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Hi Tony,
>Glad to hear it. Please form an orderly queue :)
I'll join behind Karnak so we can talk shop while we wait ;-) Will your new book be available from Amazon (like "Rapid Fire" was)?
Regards,
Henning (HoHun)
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HoHun,
I'm not talking about AP 20mm shells. I'm talking about the difference in an HE shell that explodes on, or near, the surface like the German Mine shells compared with an HE shell that explodes deeper in like the British Hispano HE rounds.
Both explode, but I wouldn't entirely dismiss the effectiveness of the British HE rounds. It seems to me that you are thinking of them as simple AP rounds.
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Originally posted by HoHun
Hi Tony,
I'll join behind Karnak so we can talk shop while we wait ;-) Will your new book be available from Amazon (like "Rapid Fire" was)?
Regards,
Henning (HoHun)
I expect so, but we haven't got around to talking about that yet.
Tony Williams
Author: "Rapid Fire: The development of automatic cannon, heavy machine guns and their ammunition for armies, navies and air forces"
Details on my military gun and ammunition website:
http://www.quarry.nildram.co.uk
Military gun and ammunition discussion forum:
http://forums.delphiforums.com/autogun/messages/
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Originally posted by Karnak
HoHun,
I'm not talking about AP 20mm shells. I'm talking about the difference in an HE shell that explodes on, or near, the surface like the German Mine shells compared with an HE shell that explodes deeper in like the British Hispano HE rounds.
Both explode, but I wouldn't entirely dismiss the effectiveness of the British HE rounds. It seems to me that you are thinking of them as simple AP rounds.
The German shells had a fuzing problem (too fast-acting) until sometime in 1941, when delay fuzes were introduced. However, even after that the greater kinetic energy and stronger construction of the Hisso shells allowed them to penetrate further into the plane's structure (assuming the fuze didn't go off too soon).
The Hisso shell generated less blast pressure but threw larger and heavier fragments around, which had a kinetic energy of their ownand copuld inflict serious damage depending on what they hit.
Tony Williams
Author: "Rapid Fire: The development of automatic cannon, heavy machine guns and their ammunition for armies, navies and air forces"
Details on my military gun and ammunition website:
http://www.quarry.nildram.co.uk
Military gun and ammunition discussion forum:
http://forums.delphiforums.com/autogun/messages/
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Hi Karnak,
>I'm not talking about AP 20mm shells.
Oh, sorry for the misunderstanding then.
>I'm talking about the difference in an HE shell that explodes on, or near, the surface like the German Mine shells compared with an HE shell that explodes deeper in like the British Hispano HE rounds.
There mine shells had a delayed action fuze that made them blow up within the airframe. This was imperative to get the full blast effect - the shell has to explode in a confined space for the greatest destructiveness.
I think it were the Hispano HE rounds that had the fuzing problems leading to detonation on the surface, not the mine shells.
The greater penetration capability probably gave the Hispano some capability against "hard" components (though a 10 g charge won't blow off the main spar, anyway).
However, with only half the explosive content, it was less than half as effective as the mine shell in destroying the aircraft's load-bearing skin. During mine shell development, it had been recognized that it was essentional not just to blow sections of skin off the aircraft, but to make the damage jump the riveting of the attacked section to weaken the adjacent sections. In that way, a larger charge could do much heavier damage than a smaller charge as it destroyed the load-bearing properties of a much larger skin area. (In the end, this lead to the 30 mm mine shell, of course.)
To get back on the topic of the MG FF: While mine shells were most effective against an aircraft's wings, their effective target area wasn't limited to it. There's one interesting Battle of Britain era photograph that shows a Spitfire which took a single MG FF/M hit into the empty rear fuselage. The entire tail got "soft" and was bent to the point of wrinkling the aluminium skin. Though the pilot got the aircraft down safely (no doubt with great care to avoid any hard manoeuvres), the plane was beyond repair and had to be written off.
Regards,
Henning (HoHun)
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Yes, Mgeschoss relies solely on blast effect, not much fragments to talk about. It was very thin walled projectile with maximum amount of HE.
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Originally posted by HoHun
I think it were the Hispano HE rounds that had the fuzing problems leading to detonation on the surface, not the mine shells.
Yes they did, but according to British tests of the German ammo I have seen, the German 20mm HE had exactly the same problem until about 1941.
Tony Williams
Author: "Rapid Fire: The development of automatic cannon, heavy machine
guns and their ammunition for armies, navies and air forces"
Details on my military gun and ammunition website:
http://www.quarry.nildram.co.uk
Military gun and ammunition discussion forum:
http://forums.delphiforums.com/autogun/messages/
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Originally posted by illo
Yes, Mgeschoss relies solely on blast effect, not much fragments to talk about. It was very thin walled projectile with maximum amount of HE.
Not quite - it did produce fragments, but they were small and high-velocity. In the right circumstances they could do alot of damage themselves.
Tony Williams
Author: "Rapid Fire: The development of automatic cannon, heavy machine
guns and their ammunition for armies, navies and air forces"
Details on my military gun and ammunition website:
http://www.quarry.nildram.co.uk
Military gun and ammunition discussion forum:
http://forums.delphiforums.com/autogun/messages/
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What were the fusing times for the Hisp. shell then?
Why should a quick mechanism be always bad? Imagine you have a delay that is equal to a travel way of 50cm, ~0.5yard. If you fire at an aircraft from behind the shell may enter the fuselage and penetrate deeper, though not much deeper.
But what happens when you fire at a fighter from above (imagine he is banked 90° in a turn) ? When you hit a wing, the shell will leave the wing on the other side before exploding right? Even bomber wings aren´t 0.5y thick, right? The width of a fighter fuselage isn´t much larger. So if you don´t have the luck to hit the main spar you get only a nice little hole.
niklas
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Nice picture illo! Can you show us also "chart1", the left part? Thx!
Did you notice that the "Sprenggr. ÜB" is listed in the row GB/USA and seems to be a Hispano Shell? The same designition can be found in the trajectory pictures for the FW190. That´s really strange
niklas
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Hi Niklas,
>Did you notice that the "Sprenggr. ÜB" is listed in the row GB/USA and seems to be a Hispano Shell? The same designition can be found in the trajectory pictures for the FW190. That´s really strange
Good observation! Looking at it more closely, I seem to read it as actually "Sprengr. Üb." like "Übungsmunition" ('practice ammunition'). I've seen the same abbreviation for German 20 mm before.
The drawing doesn't indicate any fuze, and though the shell looks like the flat-nosed explosive shell, there's no indication of any filling either on the drawing or in the table.
I'd say this is an inert projectile for practice (and testing) purposes.
That you found the same designation on the trajectory diagram for the Fw 190 seems logical since inert shells were more useful for test-firing as they merely punched neat holes :-) That's much better for checking the weapons' alignment than having your targets torn to pieces by explosive rounds.
Regards,
Henning (HoHun)
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Hi Tony,
>Yes they did, but according to British tests of the German ammo I have seen, the German 20mm HE had exactly the same problem until about 1941.
That's interesting, I hadn't read about that before. Are we talking about mine shells or regular HE shells now?
I guess if we're talking about mine shells, the problem must have been less common since they remained in service while the Hispano HE shells apparently were withdrawn for a while.
Regards,
Henning (HoHun)
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Originally posted by HoHun
That's interesting, I hadn't read about that before. Are we talking about mine shells or regular HE shells now?
This is from report AVIA 6/13387 in the PRO: "Firing Trials of German 20mm HE/HEI from Bf 109F-2".
Among other things, the report noted "no evidence of a delay action to the fuze". I presume that this applied to both HE-T and M-Geschoss.
Tony Williams
Author: "Rapid Fire: The development of automatic cannon, heavy machine guns and their ammunition for armies, navies and air forces"
Details on my military gun and ammunition website:
http://www.quarry.nildram.co.uk
Military gun and ammunition discussion forum:
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Originally posted by niklas
Why should a quick mechanism be always bad?
Any fuze setting has to be a compromise, taking into account the most likely attack angle. In most cases against fighters, this would have been very close to directly behind, with the fuselage being the target. Some delay would therefore have been an advantage.
Slightly OT, but I understand that the Israeli Air Force was disappointed with the performance of the DEFA cannon in their planes in the 1960s-70s conflicts. It turned out that the French ammo had been designed for hitting Soviet bombers, so the fuzes had such a long delay that they didn't detonate until they were clean through the fighters they were shooting at.
Tony Williams
Author: "Rapid Fire: The development of automatic cannon, heavy machine guns and their ammunition for armies, navies and air forces"
Details on my military gun and ammunition website:
http://www.quarry.nildram.co.uk
Military gun and ammunition discussion forum:
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The fuselage must be the target when your goal is to set the target to fire, what was at the beginning the most successful method to destroy it. But this changed with the M-shell. Now the structure became directly the target.
Do you know the fuzing time for a Hispano HE-shell? If it was equal to a travel way of 1-2 yard, it should be pretty useless when hitting a wing from above or a fuselage from the side.
I know from 2 german fuses for mineshells, one had a delay of only 36us, the other 275us.
niklas
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I'm sorry, I don't have any specific information about the delay time on the Hispano fuze.
It's worth pointing out that 80% of RAF Bomber Coomand losses were attributed to fire rather than structural damage. The "I" part of HEI was very important; in fact the last type of M-Geschoss 20mm ammo tried was nearly all I with just a small bursting charge of HE.
Tony Williams
Author: "Rapid Fire: The development of automatic cannon, heavy machine guns and their ammunition for armies, navies and air forces"
Details on my military gun and ammunition website:
http://www.quarry.nildram.co.uk
Military gun and ammunition discussion forum:
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Henning wrote:
A typical WW2 fighter might present as little as 10% critically vulnerable surface..
I believe this is wrong. I did a rough measurement of the presented target area of a spitfire from a cross-sectional drawing presented from the front quarter (“The Great Book of World War II Airplanes”, various Authors, 1984 Zokeisha Publications, Ltd. pg. 284). The major structural components take up approximately this much of the presented area:
Forward fuselage: 19%
Cockpit: 9%
Read fuselage: 21%
Wings: 44%
Tail: 7%
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Total: 100%
The “critical targets” take up approximately this much of the presented area:
Engine/glycol/coolant jacket: 9%
Oil Tank: 1%
Pilot: 4%
Fuel: 7%
Oxygen tanks: 1%
Ammo boxes: 4%
Fuel pipes, cables etc.. : 1%
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Total: 27%
From a more typical attack angle of the dead 6 of a fighter, a larger cross sectional percentage of the target (as much as 50% or 60%) contains a critical target. From the dead 6 approximately 1 in 2 hits on a fighter would be heading towards something potentially catastrophic (given sufficient penetration power), such as an ammo box or the engine or pilot.
Hooligan
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Hi Tony,
>It's worth pointing out that 80% of RAF Bomber Coomand losses were attributed to fire rather than structural damage.
I think that figure may be the best possible estimate, but the difficulties of arriving at accurate figures for the resons for bomber losses over enemy territory at night must be considerable. (Just think of how long it took the RAF to recognize the "Schräge Musik" attacks as what they were.)
And catastrophical damage to a bomber would typically involve fire, too - no matter if it was the cause of the catastrophical damage or the result.
Regards,
Henning (HoHun)
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Hi Tony,
>Among other things, the report noted "no evidence of a delay action to the fuze". I presume that this applied to both HE-T and M-Geschoss.
Niklas' figure of 36 micro seconds is a very short fuzing delay that will only allow the shell to travel a few centimeters before detonating (which suited the damgage mechanism of the mine shell). I could imagine the RAF verdict is based on the mine shell's failure to match the RAF's expectation of a substantially longer delay.
Regards,
Henning (HoHun)
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Hi Hooligan,
>I did a rough measurement of the presented target area of a spitfire from a cross-sectional drawing presented from the front quarter (“The Great Book of World War II Airplanes”, various Authors, 1984 Zokeisha Publications, Ltd. pg. 284).
Good approach!
Note that my lower figure for critically vulnerable area (10% versus 27%) comes from the requirement for an immediate kill raised earlier in this thread, while you've included targets that lead to the aforementioned "slow" kills.
To arrive at a complete analysis with your approach, we'd need to assign kill probabilities for each of the critical targets you mentioned to get the overall kill probability. For example, the engine is a pretty hard target and has a good chance of surviving even a direct hit, and the pilot armour is going to stop a certain proportion of the attacking projectiles (even if they're 20 mm armour piercing).
For comparison, the Luftwaffe considered 6 x 20 mm enough to kill a fighter. That's an average probability of kill of 17%. You're starting with 27% now, presuming a 100% probability of kill per component. By adjusting the Pk for each component to a realistic value, you can check how well your model compares to the Luftwaffe's analysis.
Regards,
Henning (HoHun)