HiTech, you may check real MG-FF dispersion here

[Tony Williams]

Originally posted by GScholz
The "bounce away" myth is just that ... a myth. The skin of aircraft is in no way strong enough to deflect even the guns with lowest of muzzle velocities. Most pistol rounds would penetrate at 50-100 yards even at extremely shallow angles.

I have to question that. If bullets - and even battleship shells -  will skip off water if they hit it at a shallow enough angle, then a stiff alloy skin should be capable of deflecting very shallow-angle strikes. It was one of the reported problems suffered by USAF F-86's in Korea; their .50 cal bullets kept skipping off the tough skin of the MiG-15s.

Tony Williams

[Krusty]

Not so.

The Sabers in Korea had 50cal rounds that HIT but failed to blow their targets apart. Many a mig returned home with a huge freaking hole in its wing, tail, fuselage, or "insert part here". The 50cals HIT, but due to the tough-as-friggin'-nails Soviet jet construction, the planes could withstand almost anything.

Consequently, that is why later US aircraft began carrying cannon.

Also, the 50cal incendiary round could penetrate a large steel plate with ease. There was a post long ago on the forums that had detailed info about that, and a picture profile of a 50cal round doing so. Can't be arsed to search for it (was 3+ years ago, probably gone)

[Tony Williams]

I have no doubt that the .50 API can penetrate armour plate - in fact, around 20-25mm of it, if it hits it dead-on (i.e. at short range and 90 degrees impact). I also have no doubt that it shot many holes in the MiG-15s.

However, you are ignoring the question of striking angle, which is crucial. Even at short range, the .50's penetration of steel armour drops from 20+mm to only 5mm if it hits at 30 degrees. As the angle of the hits gets shallower, so the penetration falls off at an ever-increasing rate.

Any bullet which strikes a glancing below (i.e. it isn't the point which strikes first, but the body of the bullet) has very little penetrative power, and in those circumstances a stiff light-alloy skin could indeed deflect it - and did so, according to first-hand reports I have read from Korea.

Tony Williams: Military gun and ammunition website and Discussion forum

[butch2k]

Some facts

[GScholz]

Originally posted by Tony Williams
I have to question that. If bullets - and even battleship shells -  will skip off water if they hit it at a shallow enough angle, then a stiff alloy skin should be capable of deflecting very shallow-angle strikes. It was one of the reported problems suffered by USAF F-86's in Korea; their .50 cal bullets kept skipping off the tough skin of the MiG-15s.

Tony Williams

It's quite simple: Water provides more resistance than a thin sheet of aluminium at whatever angle. A sheet of aluminium can only offer a finite amount of resistance before breaking and yielding to the projectile. Water (depending on depth) offer an almost infinite amount of resistance and will continue to change the vector of the projectile until it either flies back up out of the water, or loses so much energy that it sinks. The projectiles do not really "skip" of the water surface, but rather dive under it and gets skewed back up by hydrodynamic forces. As someone pointed out, a bullet has an aerodynamic profile that creates lift.

The MiG-15 "flying tank" is also a myth. The .50 cals didn't skip of the though skin ... the MiG was simply so ruggedly constructed that it could take incredible amounts of damage and keep on flying, and the jet fuel didn't burst into flames as easily as the WWII aviation gas the US pilots were used to (many of them were WWII veterans).

[Tony Williams]

The graph above doesn't help as it only goes to 40 degrees from the vertical - what I'm interested in is what happens when you reach the 'glancing blow' stage - i.e. at 80+ degrees, such as you would get when hitting the fuselage skin of a plane you were firing at from dead astern (or close to it).

TW

[brady]

Very Interesting, How I wounder would Fused Shels such as say a Ho-5 20mm react in such an instance, would the impact from the strike in a situation whear a glancing blow ocured that would defelect a 50cal round, be suficient to cause the detonator to...well detonate? And Not just the mechanical fuses, how would the chemical detonator on again a later Ho-5 HEI round react?

[Tony Williams]

There was always a certain percentage of HE rounds which failedto detonate on impact. In many cases, this would have been because they hit at too shallow an angle. The later British Hisso used an air-column fuze (as did some of the Japanese shells) which required the nose to hit first to work. Other fuzes used inertia, which required the shell to be slowed down suddenly as when hitting something. Again, a graze might not have set it off.

Getting a fuze to be sensitive enough to work properly with graze hits while still being safe to fire was not easy - it still isn't today.

TW

[brady]

TY Tony, I was woundering though on the PETN fuse in the later model Ho-5 cannon rounds, would they of neaded to impact dead on in order to work? or would the shock from the crazing of been enough to set them off?

p. 181 Flying guns, their is an image of the round I am refering to.

[Tony Williams]

Well, you have to bear in mind that this fuze has no safety devices so needs to be insensitive enough to tolerate being slammed up a feed ramp as it's chambered. I don't think it would work with a grazing hit.

TW

[brady]

TY Tony. This is all very interesting realy, espichaly since one would think that a lage percentage of potential hits from a following posation could be grazing.

[GScholz]

Tony, I believe the German HE and HE(M) shells had a rotation activated safety and self-destruct. I don't know about other shells though.

[Tony Williams]

German fuzes for home defence fighters had a self-destruct mechanism (which normally operated at 800-1,200m) but they used simpler contact fuzes for ground attack.

TW

[Charge]

The cannon was already a potential choice for fighters in WW2 but I guess the reliability of US hispano was not good enough and the rate of fire was not considered enough in jet dogfighting.

Considering the distances and speeds and durability of jet airframes I can easily believe that the bullet penetration was a real problem as well as the bullet being too light to be effective at those speeds as the bullet was constatly passing transonic speeds which probably caused them to be very inaccurate in longer ranges.

However, the combined rate of fire of 6x'50 cal and their "shotgun effect" was usually enough to score several turbine hits which were alone devastating. Their power was surely enough from close range but I'd believe it was very hard to get very close to an enemy a/c in jet dogfight.


Slightly blunt tip is good for penetration as it "cuts" through the skin of the a/c even in shallow angles so I'd think that is why it was a common shape in WW2 20mm grenades.

-C+