Weapon experts, question for you

[Vulcan]

Can you please comment on this statement:

Real world WWII testing showed that at flat angles of impact (0 -> 3 degrees on average) little actual damage would be done, even to thin aluminium wings, fuselage and tail surfaces. Real world WWII testing determined as high as 90% total ineffectiveness of such bullet strikes.

Look at it this way. You fire 600 rounds at the target. Let's be generous and say 100 of them hit (that IS generous even though many players think ALL their rounds hit, they are very wrong) ... if of those 100 80 of them strike at near flat (up to 3 degrees) angle to the target, that's 20 rounds left that actually do any effective damage.

20 out of 600 would produce a "WTF !!" state of mind if you were the shooter and you felt you got all 600 rounds into the target and expected the equivalent of 600 rounds effective damage from those 20 rounds.

Trust me, if you got an angle of strike greater than 3 degrees on the target it will do exactly what it's intendded to do, every round that achieves such a strike, and yes, even from dead six o'clock ... but only if the angle of strike is higher than 3 degrees. From dead six, you don't have a lot of chances to beat that angle of strike limitation, and a lot of your rounds are missing even though you may think otherwise. You have no real idea how many are striking, you just see debris that is easily overwhelmed by your expectations.
   

The scenario is dead 6 shots from reasonable close range, the theory above is that 90% of shots are richocheting/deflecting off aluminium wings instead of penetrating them (7.62 and 20mm rounds).

[Wotan]

There was a thread on another forum (I can’t for likes me remember where) that talked about this very thing. It was suggested that dead 6 shots produced a large number of "grazing ricochets".

There was mention of using a slight off angle to increase the target profile and to ensure a better angle of impact. I don’t think there was any talk of "percentages" but just some anecdotal pilot descriptions.

Maybe Tony Williams has some info.

[storch]

When Kermit Weeks had his excellent Museum at Kendall Regional Airport in Miami, Florida they had a Ki-61 which had been dragged out of the jungle in New Guinea.  The plane was displayed in an as is condition, I believe it was slotted for restoration but a date had not been set.  This aircraft had considerable battle damage.  Two things struck me as odd.  first was that the aircraft's aluminum skin was so very thin (.030-.035?) and secondly that many of the rounds fired at it did not penetrate that thin skin.  You could see where they had glanced off leaving the metal stretched and dented but not broken.  Very cool display.

[Krusty]

If it's so old, and was drug from a jungle of all places, how do you know those dents are from bullets?

Just curious

[storch]

Originally posted by Krusty
If it's so old, and was drug from a jungle of all places, how do you know those dents are from bullets?

Just curious

The aircraft was in very good shape (well good shape considering it was shot down and crashed in the jungle)  The bullet holes/indentations were visible on the fuselage and the wings.  They were clearly bullet riccochets because from years of shooting stuff I know what a bullet riccochet off of sheet metal looks like.  From bbs glancing off of the side of beer cans to 30.06 glancing off of an abandoned junk car's hood the indentation is distinctive.  IIRC it was the 4 12.7mm armed model again IIRC all 4 MGs were in the wings.  The Museum was called the Weeks Air Museum and I was a dues paying member allowing me the opportunity to visit any time I wanted and pretty much walk around unsupervised.  I had the opportunity touch, feel and sit in many interesting aircraft.  I'll check and see if they have any mention of that aircraft on their site at Fantasy of Flight in Polk City Florida.  I just contacted them via e mail.  the website is http://www.fantasyofflight.com  the Ki 61 does not appear in the current collection roster.

[Holden McGroin]

If you are flying directly behind an opposing fighter and open fire, you are shooting at the sharp edge of the knife, not the broadside of a barn.

The angle of bullet impact on most all surfaces you could hit would be very close to parallel to any given surface rather than perpendicular. A near parallel strike just deflects a bullet only absorbing the energy that is required to redirect the bullet path.

Like in judo the effort to redirect is much less than required to absorb.

Even a shot perpindcular to an aircraft surface will likely only puncture the skin, causing minimal damage, as most of the volume in an a/c is empty space. Pop a hole through both sides of the fuselage, and unless a critical system is damaged, the plane will likely be able to fly home.

Take a random shot at the broadside of a barn and the barn will remain standing.

[Vulcan]

Interesting, I understand the concept but I would have thought the energy from close shots would have overcome the stressed skin?

[Holden McGroin]

A bullet will skip off the surface of a pond when at a shallow enough angle and all it would need to do is break the surface tension of water.  Yet it skips.

[SunTracker]

I remember reading about a corsair pilot who saw his rounds richocheting off the wing of a zeke.

[Tony Williams]

I don't have any data on this, and I've never heard of any tests being carried out, but I have read anecdotal evidence of grazing hits being deflected, and it seems entirely reasonable to me. The penetration of projectiles falls off with increasing steepness as the angle of attack reduces. Once it's the body of the projectile which strikes, rather than the point, then I would expect deflections to start happening.

Of even more significance is the fact that the operation of cannon shell fuzes also becomes increasingly unreliable as the striking angle reduces. That's still the case even today.

Tony Williams: Military gun and ammunition website and discussion
forum

[Pongo]

I dont know about 80% of them not penetrating or not fusing though. Certianly some% but 80?

[Tony Williams]

I don't know. I suspect that it would depend to a degree on the construction of the target plane - and the shape of its rear end. Obviously, a bomber with a tail turret will present a much better target to a rear attack. Fabric-covered control surfaces (which were common even with basically metal planes) would also not deflect the projectiles.

The anecdotal example I know of was i the Korean War when the F-86's .50 cals were said to often graze off the MiG-15.

TW

[storch]

I just received a reply from Paul Stecewyzc of Fantasy of flight re: the Ki 61.  The airplane is still in the same condition as it was 18 years ago and is at their facility here in Miami.

[GScholz]

Bullets do not skip off water, nor do they skip off thin sheets of aluminium. However the skin on the wings and most fuselages is curved and therefore a projectile may very well just grace a small portion of the surface, leaving a furrow that makes it look like the projectile skipped off.

Originally posted by GScholz
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).

[storch]

Originally posted by GScholz
Bullets do not skip off water, nor do they skip off thin sheets of aluminium. However the skin on the wings and most fuselages is curved and therefore a projectile may very well just grace a small portion of the surface, leaving a furrow that makes it look like the projectile skipped off.

Well one could expect that response from a person that does not shoot much.  projectiles will indeed skip across the water.  The .22 cal projectile is notorious for this.  Bombs can even be made to skip across the water.  Skip bombing was refined to produce very good results by P38 drivers in the PTO among others.  The English destroyed/damaged dams on the Ruhr with 10,000 lb skip bombs.  If the angle is slight enough to the projectile's flight path even your intellect will deflect it.