Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: Tac on August 27, 2001, 07:51:00 PM
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Dont do squat for having 4X .50 cals and 1 20mm in such a close package (guns barely 2 inches apart!).
Takes the same amount of lead to bring down a con with the 4 X.50's of a P-51B outside of convergence than a P-38 at d100.
Many times, almost always in fact, a plane begins a tight turn to avoid a diving 38, I get a clean snapshot at it as it banks, the plane is an x-mas tree from nose to tail as it passes by my nose on its turn.
Now I KNOW that at such close range I AM hitting with all 5 guns. Con flies away with no damage or a fuel leak at the most.
Id understand lag if it was some times, but almost ALL the time? I kill in snapshots with the Yak.. 2 mg's and 1 cannon all the time at d200 or less. So, whats up with the 38's guns? Same range, yet more guns, more firepower and higher ROF. Different results. :confused:
Any shot at close range should be punching a hole the size of the 38's nose, the .50's drilling and the 20mm punching the hole in.
Is there way too much dispersion or what?
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Probably dispertion. Imagine the firepower of the Lightning as being like water spraying from an adjustable hose nozzle. In AH it might be set to the "sprinkler" position. ;)
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You may get sprites, but if the cannon round missed hitting the aircraft due to gravity drop or whatever, then it would be very similar to the gunpower of a 51B.
-Puke
332nd Flying Mongrels
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not at d100 or less and your plane is not pulling and its the enemy plane that's flying by your nose during the snapshots. You hit with 5 guns guaranteed. No damage.. guaranteed. Its getting real old real fast.
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Tac from what I've seen the key to killing with .50's is to get a sustained burst on target in one location. It seems to take a 1 to 2 sec burst or more in a Pony with 6 .50's.
Lighting a con up from nose to tail will put lots of holes in the skin, but there may not be enough hits in any given location to cause major damage.
While I use snapshots a lot myself I really don't expect them to cause any major failure.
An aileron or oil line perhaps, but it's more a softening up thing. Unless you can get hits in the same location 2 or 3 times.
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Roger that Ghost. If you can hold them on one spot for a short bit of time... boom. Even buffs.
If you sprinkle 'em around, the plane keeps flying.
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So in other words, the concept of concentrated firepower =null in AH?
So much for the convergence issue and the supposed hit power of the P-38. *sigh*
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No, Tac, what I think he means is this (and I may not explain it very well, but I'll try).
When you fire, your bullets are moving in one direction. They may be moving in more than one plane of motion, depending on your aircrafts motion when you fired, but they are primarily going in one direction.
On a deflection shot, your target is moving in a different direction than your bullets are going. Say you have a really teeny burst of 4 .50 bullets and 1 20mm round that you fired at someone in a 90 degree deflection shot. Since your target is moving perpendicular to your bullets, your fire CANNOT be concentrated on one spot on the enemy plane. Even if the enemy plane runs right into your burst, he will get hit something like this
Plane takes 1 .50 to the tip of the propeller :).
Plane takes 1 .50 to the engine about 3 feet from the tip of the propeller.
Plane takes 1 .50 to an area somewhere in front of the cockpit, about 3 feet from the last hit.
Plane takes 1 .50 behind the cockpit.
Plane takes 1 20mm somewhat lower down and towards the tail of the plane.
I agree that the fire would be concentrated (better anyway) if you were right behind the target and they were not in motion relative to your guns. In that case you would probably punch an upside down, cyclops-eyed smiley face in their plane wherever you hit.
But when the target plane is in motion relative to your bullets, you just can't get the kind of concentration you need with just the 4x.50s and the 20mm. If you were in a 190A8 with those hulking 30mm cannons, you'd prolly only need one hit to kill someone- but the P38 doesn't have that sort of firepower.
I probably wasn't all that clear in my explanation, and I'm sorry for that. I am trying to explain in my own words something that Andy Bush explained to me about "bullet density" on snapshots- I'll edit it and post a link to the thread.
I can't figure out how to post a link to a different thread on the same BB. Here is what he said to me--
Andy Bush below --
Urchin
Here's a quick way to visualize the "density thing"!
Let's say the target is crossing your nose at 90 degrees angle off. You fire early enough to get your bullet stream into the target's flight path.
Now, let's say the target is doing 300KTAS...this is about 500 feet per second. And let's say the target is 30 feet long.
Imagine the projectile path as a cone that is slowly expanding as range increases....at typical convergence ranges, this "cone" may be 10-15 feet wide.
Now, we look at rate of fire and the number of guns in action...we'll go for broke and choose 6 .50 caliber machine guns that fire at about 750 rounds per minute. We'll be generous and say that equals about 80 rounds per second total.
Now we go back to the target. At 500 fps, it crosses the gun line in about .6 seconds...this means less than 8 rounds have a chance of hitting the target under the best of conditions. Not very much unless something serious is hit!
This is the reality of a snapshot...there simply are not very many rounds in the airspace that the target fly through, regardless of how many rounds are fired.
I hope this helps explain what I said. He said above that even if you fired a lot of rounds, the plane would only "fly through" 8 of them or so- and obviously they all would not hit in the same place. He meant it if the guns were in the wings, but I don't see how it'd be much different with nose-mounted guns (perhaps the hits would be closer together, but they wouldn't hit in the SAME spot).
[ 08-28-2001: Message edited by: Urchin ]
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"He meant it if the guns were in the wings, but I don't see how it'd be much different with nose-mounted guns (perhaps the hits would be closer together, but they wouldn't hit in the SAME spot)."
Thats my concern. Wing mounted guns would have most guns either miss or the bullets be hitting the plane too far apart. But when you got 4 .50's and 1 20mm firing in an area no bigger than a soccer ball... that thing should do some serious damage upon impact! Its like getting hit on the chest with the tip of a broomstick compared to getting hit with the broadside of the stick using the same impact forec. Which hurts more? Which does more damage?
On relative moving targets moving THROUGH the stream of fire, the bullets would still hit quite close together,as they were fired quite close together and did not travel at an angle (as do wing mounted guns as they travel towards convergence). The 20mm too! Im talking almost point blank range here, less than d100, its in those cases when the con's topside view almost literally fills your entire view.
Ill need to film some of this so ye can see. I just dont get the lack of punch. I can spray a con at d600 get 2 pings and it may crack open. But I fire at less than d100 and see a LOT of hits all over the plane, and no damage. Dont make sense to me. :confused:
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Do it, if you would. Film 5 or 6 fights and post a message to me so I can give you my Email address.
I DO think there are some issue with the hit sprites, I get wierd stuff happening on occasion, like I posted up in the Training Board.
You are a good stick. I've flown against you and you fly very well. I'd like to see exactly what you are describing, but on the film. Perhaps it will give me a clearer idea of what you mean.
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Originally posted by Urchin:
Plane takes 1 .50 to the tip of the propeller :).
Plane takes 1 .50 to the engine about 3 feet from the tip of the propeller.
Plane takes 1 .50 to an area somewhere in front of the cockpit, about 3 feet from the last hit.
Plane takes 1 .50 behind the cockpit.
Plane takes 1 20mm somewhat lower down and towards the tail of the plane.
I agree that the fire would be concentrated (better anyway) if you were right behind the target and they were not in motion relative to your guns. In that case you would probably punch an upside down, cyclops-eyed smiley face in their plane wherever you hit.
But when the target plane is in motion relative to your bullets, you just can't get the kind of concentration you need with just the 4x.50s and the 20mm. If you were in a 190A8 with those hulking 30mm cannons, you'd prolly only need one hit to kill someone- but the P38 doesn't have that sort of firepower.
This is not really an accurate description of the concentration of gunfire, even when the target is moving perpendicular to the shooter. Here's why:
All of the P-38's guns are fired via individual solenoids. All of the Brownings will have virtually identical "lock time". "Lock time" defines the time between the release of the hammer and the firing pin striking the primer. All of the solenoids should have nearly identical field rise times, meaning that all should pull in at the same time, give or take a few milliseconds. So, for all practical purposes, all five weapons will discharge at the same time. Thus, the first five rounds will be heading towards the target in a tight group, equal to the actual gun placement or pattern. When the arrive at the enemy aircraft, they WILL STILL BE IN THE SAME GROUPING (with the exception of the 20mm round, see below). Hence, they will strike the enemy aircraft with the same pattern. There will be no significant dispersion whatsoever, other than ballistic differences between the Brownings and Hispano. As the weapons cycle, all four browings will discharge simultaniously, with the slower cyling Hispano lagging behind. This next series of .50 cal rounds will follow about 80 milliseconds after the first group, and will arrive in a group as well. Obviously, the 20mm round will arrive later. Assuming the enemy aircraft is moving at 300mph across the shooter's path. Then, the aircraft has moved about 35 ft since the first group of rounds struck (this assumes that no attempt was made to pull lead). In all likelihood, this second group will miss altogether. Remember, machineguns fire at a specific rate, and if all are triggered at the same time, this rate can now be identified as groups seperated by the cycle time of the weapons. Think of the Browning's cycle time as a continuous sine wave. with the hispano being represented by a corresponding wave of a slightly different frequency. Therefore, for a long burst you will have two distinct patterns developing with one out of phase to the other. With multiple guns, you simply don't get the "stiching" effect seen with a single weapon or that protrayed by Hollywood. You will get groups of hits seperated by the time/distance equation.
Think of the P-38's weapons as a garden hose.
The concentration will make you very wet. Bring one gun to bear, and all are on target. This provides a downside as well. Miss with one and it's likely that you have missed with all. Wing mounted guns increase the chances of a hit, but nose mounted ordnance tends towards a greater mutiple of hits (except when at the convergence point), therefore more damaging hits should your aim be true.
There should not be any significant dispersion of .50 cal rounds from the P-38, right out to maximum range. Deflection shots will move the 20mm round(s) out of the general pattern due to reduced velocity and slower cyclic rate.
My regards,
Widewing
[ 08-29-2001: Message edited by: Widewing ]
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Ahhh, I see. Thank you for the information, Widewing :).
Even so, it would be tough to bring someone down with a snapshot, because now although although 1 "wave" of bullets would probably still hit, you are still only talking about 4 .50 cals and a 20mm shell. The other "groups" would probably miss because there are big enough gaps between the individual "salvos" (for lack of a better word) of .50 rounds, since they all fire at the same time. Is this correct or am I still wrong in some way? I don't know much about the topic, I just tried to infer something from Andy's explanation :).
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Fwiw, and I'm no AH ace, but in a turn fight or other situtations where I have to pull lead for a deflection shot I use only the P-38's .50's. If I have a dead on "6" shot I will I use them all. It usually gives me a pilot kill (well the plane blows up versus suffering other, less amounts of damage) and with the extra 20mm I usually means much less ammo used over all.
-Westy
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Hi Urchin,
here's a quote from Major Robert H. Riemensnider, who flew P-51D with the 55th Fighter Squadron:
"I had previously flown the twin-engined P-38 Lightning where the nose-mounted armament made for an ideal gun platform. Ranging wasn't the problem it was with the P-51 and other fighters which had wing-mounted armament where the fire converged. In our outfit the guns were adjusted for a point of convergence 300yd ahead where, theoretically, they gave an approximately 8 x 10 ft bullet pattern. In practice, because of the speed of closure, it was not easy to achieve that exact range when you hit the gun trigger. So there was a tendency for pilots to open fire at a target further off and hold a long burst as they closed. If you got in a correctly ranged burst, it was highly destructive. In my opinion the six 0.50in calibre guns of the P-51D were adequate for the job we were doing."
(From Roger Freeman's "P-51 in Combat".)
Due to the variance in cycle times of individual machine guns, I'd disagree with Widewing's "salvo fire" image - it took electrical priming to achieve that kind of accuracy. (Electrical priming in WW2 was only employed in German armament, though.) The P-38 really sent an inhomogenous stream of bullets towards the target. (Cycle time varied with ammunition type as well, and priming introduced an additional random factor.)
That the P-38's Brownings weren't subject to dispersion would appear to be a bit of an exaggeration, but compared to the 8 x 10 ft pattern described by Riemensnider, the P-38's pattern was smaller due to the more rigid mounting of the guns - it was "coffeetable size", as one P-38 pilot said.
In any case, you can safely rely on Andy's explanation - visualize the P-38's fire cone as much smaller than the P-51's, and you get the picture.
(Or think of two intersecting cones extending from the P-51's wings that are only slightly wider than the P-38's single one :-)
Regards,
Henning (HoHun)
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Originally posted by Widewing:
This is not really an accurate description of the concentration of gunfire, even when the target is moving perpendicular to the shooter. Here's why:
All of the P-38's guns are fired via individual solenoids. All of the Brownings will have virtually identical "lock time". "Lock time" defines the time between the release of the hammer and the firing pin striking the primer. All of the solenoids should have nearly identical field rise times, meaning that all should pull in at the same time, give or take a few milliseconds. So, for all practical purposes, all five weapons will discharge at the same time. Thus, the first five rounds will be heading towards the target in a tight group, equal to the actual gun placement or pattern. When the arrive at the enemy aircraft, they WILL STILL BE IN THE SAME GROUPING (with the exception of the 20mm round, see below). Hence, they will strike the enemy aircraft with the same pattern. There will be no significant dispersion whatsoever, other than ballistic differences between the Brownings and Hispano. As the weapons cycle, all four browings will discharge simultaniously, with the slower cyling Hispano lagging behind. This next series of .50 cal rounds will follow about 80 milliseconds after the first group, and will arrive in a group as well. Obviously, the 20mm round will arrive later. Assuming the enemy aircraft is moving at 300mph across the shooter's path. Then, the aircraft has moved about 35 ft since the first group of rounds struck (this assumes that no attempt was made to pull lead). In all likelihood, this second group will miss altogether. Remember, machineguns fire at a specific rate, and if all are triggered at the same time, this rate can now be identified as groups seperated by the cycle time of the weapons. Think of the Browning's cycle time as a continuous sine wave. with the hispano being represented by a corresponding wave of a slightly different frequency. Therefore, for a long burst you will have two distinct patterns developing with one out of phase to the other. With multiple guns, you simply don't get the "stiching" effect seen with a single weapon or that protrayed by Hollywood. You will get groups of hits seperated by the time/distance equation.
Think of the P-38's weapons as a garden hose.
The concentration will make you very wet. Bring one gun to bear, and all are on target. This provides a downside as well. Miss with one and it's likely that you have missed with all. Wing mounted guns increase the chances of a hit, but nose mounted ordnance tends towards a greater mutiple of hits (except when at the convergence point), therefore more damaging hits should your aim be true.
There should not be any significant dispersion of .50 cal rounds from the P-38, right out to maximum range. Deflection shots will move the 20mm round(s) out of the general pattern due to reduced velocity and slower cyclic rate.
My regards,
Widewing
[ 08-29-2001: Message edited by: Widewing ]
This is not entirely true. Now I dont know about what WW said about the guns firing in a synchronized fashion. Sounds like he knows what he is talking about though so I will assume he is correct. However where I do know there is error is the part where he says that all 5 projectiles from the browning's that fired at the same exact time will remain in a tight group all the way to POI. Each barrel of each individual gun has its own "personality". Every time the gun fires a wave runs through the barrel, this wave is refered to as its harmonics. Harmonics are present in all firearms, but there have been designs that reduce the "wave" or its harmonics, therefore enhancing accuracy. A notable example would be in a target rifle where the barrel has a large diameter, refered to a bull barrel. Other manufacturers mill "flutes" into exterior surface of the barrel to make it more rigid. What happens when the round is fired is this- The low order burn in the chamber propells the projectile down the barrel. at the same time the barrel harmonics has it vibrating. Where the muzzel of the barrel is in its harmonics when the projectile exits the barrel will have the greatest effect on the POI of the round. Even if you were in a vaccuum, harmanics would cause dispersion at the POI. Now take in effect the enviroment, wind, atmospheric temperature, mass produced ammo ( all ammo is NOT created equal). Handloaders take great care to measure powder charges to help alleviate accuracy problems. Now in WW2, obviously, quantity over quality, was the word for the day. Also another thing, the vibration from all those guns, and the less than rigid mounting, and the consider the AC is not the greatest platform to faciltate inherant accuracy, and you can now see that why there was alot of dispersion, especailly at greater ranges.
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*sits down with a steaming popcorn bag smeared with butter*
oh boy, we getting to the good part!
*munch**munch*
keep the info coming, im learning a lot :)
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Originally posted by -ammo-:
This is not entirely true. Now I dont know about what WW said about the guns firing in a synchronized fashion. Sounds like he knows what he is talking about though so I will assume he is correct.
There is no synchronization per se, so much as all solenoids are operated by the same switch, being energized at the same time.
However where I do know there is error is the part where he says that all 5 projectiles from the browning's that fired at the same exact time will remain in a tight group all the way to POI. Each barrel of each individual gun has its own "personality". Every time the gun fires a wave runs through the barrel, this wave is refered to as its harmonics. Harmonics are present in all firearms, but there have been designs that reduce the "wave" or its harmonics, therefore enhancing accuracy. A notable example would be in a target rifle where the barrel has a large diameter, refered to a bull barrel. Other manufacturers mill "flutes" into exterior surface of the barrel to make it more rigid. What happens when the round is fired is this- The low order burn in the chamber propells the projectile down the barrel. at the same time the barrel harmonics has it vibrating. Where the muzzel of the barrel is in its harmonics when the projectile exits the barrel will have the greatest effect on the POI of the round. Even if you were in a vaccuum, harmanics would cause dispersion at the POI. Now take in effect the enviroment, wind, atmospheric temperature, mass produced ammo ( all ammo is NOT created equal).
Okay, let's discuss these issues you raise. First, let me give you some background so that everyone will understand where I'm coming from, so to speak.
Since 1991, I have been working with major firearms manufacturers developing sensors that are installed in many different weapons. This sensor package monitors the discharge of the weapon and does several things.
1) It records the date and time of each round fired to an accuracy of .001 seconds. This data is stored in a chip.
2) The device records the angle and azimuth of the barrel. Likewise, this data is stored.
3)Some versions are used to trigger a laser (used on the Army's new I-CIDDS system).
4) all data is later downloaded to a PC or Palm Pilot, either by cable or IR transmission.
In the process of developing systems for various weapons, I have extensively tested such weapons as the Mk.43 and M-60 machine guns. Included are the M16A2, M4A1, HK MP-5 and MP-5/10. Also tested were the SigArms 550 and 551, Browning M2HB, Barrett "Light 50", M40A1, M24, Colt ACR, M249 and the Navy's Mk.38 25mm Chain Gun. I can include many handguns as well, but will save that for another time.
When these weapons are tested, they are fitted with an array of accelerometers to monitor motion, resonance, recoil force and
other phenomena associated with discharging the weapon, both in single shot and automatic mode. Frequently, we film the testing with high-speed cameras, as well as using lasers to measure distortion under load. Indeed, there is virtually no dynamic that is not measured. For example, the data stream will reveal the response time of the primer to being struck by the firing pin. Every dynamic is viewable and every functional dynamic of the weapon can observed. In other words, we can define exactly how the weapon behaves when fired. To my knowledge, no other organization has ever attempted to collect the volume of data that we accumulate on each weapon.
Now, lets look at the "personality" of a firearm.
There is no doubt that each individual weapon manufactured has unique properties that distinguish it from others of the same lot or production run. This is due to the fact that machine tolerances are not especially tight in firearms. You can find slight differences in two barrels, broached with the same tooling. You will find slightly different bore or barrel diameters through a production run due to tooling wear, contamination and variations in alloys.
Indeed, no two firarms are identical. Nonetheless, these difference are not significant. We can add to that the simple fact that most ammunition, and to a lesser degree, match grade ammunition, have a greater variance from round to round and from lot to lot than do the weapons.
Harmonics: You would be surprised at how little variation actually exists between weapons of the same type. For a harmonic resonance to disturb the path of a bullet, the barrel must be displaced relative to its point of aim. Typically, such displacement rarely measures more that a few ten-thousandths of an inch in the extreme case. Lateral displacement is minimal because there is very little vector energy directly applied to the barrel. The energy that distorts the barrel is generally reflected energy, and to a very limited extent, barrel expansion under pressure. The effect gained by free-floating a barrel is that reflected energy is not transmitted from the fore-stock into the barrel, thereby increasing lateral displacement. Such displacement can induce a deviation in the intended path of flight, but usually limited to less than an inch at 100 yards. M2HBs do not have a fore-stock. :D This does not translate into a significant deviation at 300 yards (a typical engagement distance in ACM) which could be construed to be the dispersal range that effects results.
Wind, temperature, humidity and so on, will effect all projectiles equally if fired at the same instant. Subsequent rounds may vary from the initial rounds, but there are other, more significant factors effecting them. Let's look at those factors.
Unlike most weapons, the Browning M2 operates via the energy of its recoiling barrel. The barrel moves rearward upon firing. This energy is used to unlock the bolt, which then moves rearward, dragging the empty case with it, where it strikes the ejector and flies out of the open receiver. A spring forces the bolt forward and it strips off a new round from the belt as the bolt closes and is locked in place. In terms of repeatability, the M2 is considered a very tightly locked system. Its inherent accuracy can be understood when we realize that unmodified M2HBs were used for extreme long-range sniping in Vietnam. These weapons were fitted with Unertil or Redfield telescopic sights, the same issued for use on Remington and Winchester sniper rifles. With a little practice, it is a simple process to squeeze off a single shot, while not disturbing the aim point. Kills were recorded at ranges easily exceeding 1,000 yards. Within that context, we know that a properly maintained M2 will provide superb accuracy and that harmonics are not a significant contributor to dispersal.
So what is?
That's easy to answer. The aircraft itself is the major cause of any dispersal. Moreover, we can lay much of the blame to the fact that aircraft are moving through a fluid in three axis. These aircraft will suffer motion from recoil, but generally it is uniform, and it the case of the P-38, very close to its centerline axis. Aircraft suffer from motion in pitch and yaw, and to a lesser degree, roll. Yet, the P-38 is a very stable gun platform for several reasons.
1) Having the guns as near to the centerline as possible reduces recoil induced pitch-up too. Unlike wing mounted guns, the nose mounted weapons do not induce significant yaw, especially problematic if one gun should jam in a wing mounting.
2) The P-38 is also very stable in its roll axis, far less jittery than most single-engine fighters and not subjected to torque.
3) Likewise, the Lightning has greater stability along its pitch axis, due to the long moment arm of the elevator. This is a fighter that needs very little elevator trim.
Another factor is the variation in the ammunition. Slight differences in the powder drop, bullet weight, dings and dents in the jackets, crimp pressure and several other factors conspire to vary both velocity and accuracy. Again, I must emphasize that these variations will not result in inaccuracies greater than a few inches at normal engagement ranges.
Mount rigidity: All airborne gun mounts have a degree of flex. However, any movement can be measured in thousands of an inch and is usually found along the barrel's axis. This is more a result of wear and stretching of metal. Lateral diplacement and yaw motion is minimal, simply because there exists very little energy in vector.
One last factor. Boresighting. Every fighter gets boresighted on a regular basis. Pilots have their favorite setups. The P-38 can have its guns set to converge at a theoretical point, or they can be sighted parallel, with dispersion being minimal on the sighting range. Either way, dispersal is not significant at the ranges typically encountered in WWII ACM.
Handloaders take great care to measure powder charges to help alleviate accuracy problems. Now in WW2, obviously, quantity over quality, was the word for the day. Also another thing, the vibration from all those guns, and the less than rigid mounting, and the consider the AC is not the greatest platform to faciltate inherant accuracy, and you can now see that why there was alot of dispersion, especailly at greater ranges.
Note that I have not disputed that dispersion is greater at extreme range. However, we should be confining our discussion to "effective range", distances under 1,000 ft. Moreover, in a snap-shot situation, dispersion is not an issue as only the first group of rounds is in question. Unless, the pilot trys to pull lead and let the enemy aircraft fly through the stream. In such cases, maneuvering, more than any other factor, will create a cone of dispersal, wherein the weapon, ammuntion or mounting are not of great significance. The greatest disperser of fire is the motion of the aircraft, which is never anywhere near as precise as the accuracy of the weapons themselves.
My regards,
Widewing
[ 08-29-2001: Message edited by: Widewing ]
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All of the above being true (And it sounds like it's close enough to call it that).
My orginal point still stands, it takes more than a few .50 bullets striking in any given part of an aircraft to cause catastrophic failure. Even if 4 of them are hitting within say a 2 foot circle. It's not the same as haveing all the bullets of a 1 second burst land in that same circle. Your simply not going to get enough damage in one area to do the trick.
Sure we've all had the 1 shot to the head pilot kill, both giving & recieving. But frankly it doesn't happen that often.
Overall while they may be harder to hit consistantly with, the 20mm will do more damage in a snapshot situation. Especially if you have 4 of them.
Does that mean the P38 isn't lethal, no, of course not. Does it mean you shouldn't take snap shots? Again no, hit em where you can when you can. It all adds up in the end.
However, if I can I will aim at the same spot on a plane. If I can get hits into the left wing on my first pass, I'll continue to try to hit the left wing. The longer you can keep hammering on one part the better your odds are that it will fail.
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Well you certainly have alot of experience in this matter.
I am only an avid metallic reloader. Just HIPO hunting rifles and target stuff. All amatuer. But I have read much and burned alot of powder. I have strove to make my stuff as accurate as possible and have done OK considering the measely amount of money (thats relative of coarse) I have invested in my firearms and equipment.
You touched on the tooling used to manufacture barrels. This is very true. For others benefit who may be following this thread, as a tool is used.. it wears out. Manufacturers have a tolerence window beyond which the tool cannot be used to safely mill a chamber or a bore of a barrel. The firearms have to be within S.A.M.I specs. If a gun was created when the tool was near the end of its useful window then you most likely have a loose chamber and bore. This often will hinder the gun from being as accurate as others like it . However there are exceptions. Now to stay on topic with the browing M2..
My old winchester M70 from a bench, with handloads it likes (same lot number) can group inside an 1.5" at 200 yards. At 400 yds this equates to a 3 inch group. I also owned a small carbine chambered in 5.56 mm. This rifle on a good day could not a keep a group smaller than 7.5- 8 inches at 300 yards from a rest. This is with ideal conditions. I say that with AC mounted Machine gun that one gun cannot produce groups anywhere near that. I would go as far to say that each individual gun may produce 12-15 inch groups at 300 yds. Now this isnt really a great big deal when you consider the size of the target. It is still a very dense concentration of fire at that range. But my orifgional point is that there is significant dispersion at effective combat ranges. Now where I define significant is that figure of 12-15 inches at 300 yards. You may not consider this significant. All the factors you related to contribute to this dispersion, from the AC itself, the guns mount, variation in ammunition, defects in the ammunition, etc..
It may well be what I call significant dispersion is not significant to you. For a fact 6 wing mounted 50's bore sighted at 300 yards hitting at the intended conversion point will be destructive, as will the P-38's 5 nose mounted 50's.
<S>
[ 08-30-2001: Message edited by: -ammo- ]
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300yrds? 1000ft?!! come on, we all know alotta shooting takes place in the MA further down range than that +)
Hell some guys have convergence set at 450+yrds
SKurj
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Hi Ammo,
the oscillations of the mounting structure generated by heavy rapid-fire weapons had a much larger impact on dispersion than the ammunition.
Here's a quote from the "Baade Report" on the Junkers company in WW2 which was prepared by the East Germans for the Soviets in 1946:
"[...] When the weapon operated properly functionally after these corrections [of basic functional problems], the tests commenced with pattern shooting. With patterns of 1 x 1 m size, except for few stray shots, for example fired from a twin mount (2 x 20 mm MG) for night fighter use, the requirements were considered fulfilled. Additionally, experience showed that the patterns were better when the mount was mounted to the airframe than when it was used on the range as isolated part. If the pattern was satisfying in this sense, the mount was mounted to the airframe and tested on the company's shooting range again. [...]"
Clearly, a 1 x 1 m pattern at a mere 100 m is considerably worse than the 1' at 300 yards you've been experiencing! I'm sure that the same 20 mm cannon would give a much better dispersion firing single shots from your rest - rapid fire and flexibility of the mounting are responsible for the difference.
The Baade Report also contains the gun adjustment procedure for the Ju 87 (late model, equipped with 2 x MG151/20). The guns were considered to be adjusted correctly if an uninterrupted burst of 21 round from each gun resulted in a pattern of not larger than 0.7 x 0.7 m^2.
The pattern size seems to have been smaller when the aircraft was in flight since it didn't oscillate as readily as when jacked up on three points ("airframe harmonics" ;-). Dispersion was still much greater than one would expect from experience with semi-automatic or single-shot rifles though.
To bring the topic back to the P-38, it would be highly interesting to have a look at the gun adjustment procedure used for this aircraft. Unfortunately, the "Warbirds Tech" volume on the P-38 does only reproduce the first page of this procedure, which provides the bore sighting template but neither the test firing details nor the allowed dispersion.
In any case, the P-38 held a reputation as excellent gun platform, and I'm confident that this reputation was well-deserved.
Regards,
Henning (HoHun)
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Thx henning, great stuff.
I believe that the actual mount and the vibration of the gun when firing has the greatest effect on dispersion, and that group size does not surprise me. I dont have proof of what kind of pattern the different AC's gun packages were capable of, so that was refreshing.
In the world of target shooting, the shooter, the gun itself, and the consistency and quality of the ammo are paramount in great shooting. In combat AC, those are miniscule in comparison to the effects you mention.
<S>, thank you
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p51B, target at d800, gun convergence at 250. Fire. Con receives about 8-10 hits all over the plane.BOOM.
P-38, target at d800. Same result..although all 4 .50's should be hitting target at convergence and each hit should be doing much more damage than the p-51b's hits.
It was said earlier that wing guns increase the chance of hitting something while nose guns increase the damage per hit (but reduced chances of hits).
Maybe its the AH damage model? The highly dispersed p51's guns hitting all over the place until 1 round hits "the spot" vs the concentrated p38 guns hitting in the same spot till it blows off? We have seen that AH planes lose entire parts of the plane with a mere touch of a single 50cal bullet. Maybe that explains why extreme close range burst from 38 guns in 1 spot many times do squat when compared to a mid to long range short burst?
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Tac are you on crack?
The firepower on the P-38L is probably my favorite in all non 2x+ hispano planes.
Maybe you are holding back on the trigger. With 500rpg you should hit them hard.
The guns on the P-38 are like a chainsaw if you know how to use them. They will make quick work of any target even in deflection shooting.. at least, when I use them.
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Plus, the P-38 is such a stable gun platform that its almost impossible for me to miss in it.
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someone put animal's leash back on, his dominatrix is looking for him!
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8-10 hits at D800 and boom? Perhaps if you kill the pilot. I need about 6-8 hits of 20mm at D250-300 to destroy a fighter, no way 8 hits of 50" at 800 yards can do serious damage.
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boom=tail or wing comes out or you make it blow up (blow up=rare at least, but it happens).
In short, you kill it.
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okidokie
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Tac, are u running aces with v-sync off? You are the only person i've met that seem to think running with it on causes rubber bullets... when in fact the opposite is true..
SKurj
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neg skurj, I had heard that with it off caused rubber bullets, even tried it, same result with either thing. Im not saying the guns dont do damage, of course they do. Im just saying that its not proportional to having the firepower concentrated in such a tight spot.
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Originally posted by Tac:
But when you got 4 .50's and 1 20mm firing in an area no bigger than a soccer ball... that thing should do some serious damage upon impact!...
On relative moving targets moving THROUGH the stream of fire, the bullets would still hit quite close together...
Sorry but your bullets would NOT be hitting close together. Even at close range, the spread of the rounds landing on the bandit would still be large because of the high rate at which he crosses your path. 4 mg's and 1 cannon cannot get enough lead in the air to guarantee a fatal hit when the target is not held in your bullet stream. Think of how long the bandit is flying through your bullet stream. 0.5 sec? 0.1 sec? less? How many rounds does your plane fire in that time? 20? 10? How many of them land at the same place? I think it is pretty reasonable that only a lucky hit will down a plane under such circumstances...
Then again, I might be wrong. :)
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Widewing, would there be any difference (as far as dispersion/lead concentration) on a P-38's .50's at 200yds when compared to 1000yds? At 1000 yds will the 4 bullets still hit "as one"?
Also, do all 4 .50's on the 38 fire at the same time or did they fire 1 by 1 (albeit milliseconds apart from each other)?
Finally, you know where I can get a copy of the whole set of "HANGAR FLYING" magazine that was issued to 38 pilots during the war?
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HT just said that the current .50's have twice the dispersion they should have. I think the answer lies there.
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Originally posted by Tac:
Widewing, would there be any difference (as far as dispersion/lead concentration) on a P-38's .50's at 200yds when compared to 1000yds? At 1000 yds will the 4 bullets still hit "as one"?
Also, do all 4 .50's on the 38 fire at the same time or did they fire 1 by 1 (albeit milliseconds apart from each other)?
Finally, you know where I can get a copy of the whole set of "HANGAR FLYING" magazine that was issued to 38 pilots during the war?
Normal dispersion can be assumed to be related to normal accuracy. Since a well maintained Browning M2 should group its round at something less than 2 inches at 100 yards, I imagine that normal dispersion cone per gun at 1,000 yards should be in the area of 24 inches. If the quality of the ammunition is consistant, all the rounds fired simultaneously should arrive within a very few milleseconds of each other. You should realize that virtually all of the dispersion cones will overlap at longer ranges.
Since all the firing solenoids are switched at the same time, and because each solenoid will pull faster or slower than any other (we're probably talking about microseconds), it is not possible to accurately guess what the firing sequence is. Nonetheless, I feel safe saying that for all practical purposes, they fire at the same time.
As to your last question: I do not know where you can get a full set of the magazines.
My regards,
Widewing
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Originally posted by Tac:
Many times, almost always in fact, a plane begins a tight turn to avoid a diving 38, I get a clean snapshot at it as it banks, the plane is an x-mas tree from nose to tail as it passes by my nose on its turn.
Well it's exactly the same with a P47 and I have 2 times more of those. I think it's the disavantage of the non-conon planes. Take a Niki/F4C/FW, the same x-mas tree will rip a wing.
In those shots with the P47 I see usually 5-8 pings, but with canons I see 3-5 pings, it's probably the rate of fire.
(I'm not criticizing anaything here, I'm just telling my experience).
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Hi Tac,
The vibrations induced by multiple rapid fire weapons lead to a dispersion that's far greater than the individual weapon's error, and the uneven firing sequence of unsynchronized weapons contributes to this.
I've not seen any figures for typical variation of the cycling peroid of machine guns, but I'd say it's great enough to turn the bullet stream into a random sequence within seconds. You can watch it happen on old films showing Il-2s strafing ground targets: One second, both wings spit flames at the same time, the next second they alternate :-)
I think Widewing is accurately describing the first salvo when the gun mounting is in rest. Probably dispersion ramps up to the full value a few cycles after that, but I'm speculating here. Probably the RAE report on their vibration problems with the quadruple machine gun turrets would give the details ;-)
I think for the P-38, the service manual describing the gun calibration procedure would give the desired result with regards to dispersion, so we could be able to find out if we're lucky and someone discovers a copy of that manual.
Regards,
Henning (HoHun)