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Ballistic .50 cal

H

harrytos23

Student
Nov 6, 2024
22
Hi there!

I am trying to calculate how thick it needs to stop a 50 BMG AP caliber using AR500 plate. I used the formula that DoD published and I was able to get that it needs 0.554" plate to fully stop it.
1747860245925.png
My question now is, since we're using only 1 plate of 0.50" thk of ar500, in theory the bullet will go through the plate. I am wondering if there's an accurate way to calculate the velocity after passing through the first plate.
 
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I think a theoretical number is possible to calculate, but in reality you will have some not quite make it through and some will likely still be going several hundred feet per second. So, not really "accurate" in my estimation.
 
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A fairly ghastly approach would be to assume a constant force on the bullet as it penetrates. Then you know that F*Ts=1/2*m*Vo^2

So with your thinner plate thickness T1 using F, as worked out above

1/2*m*v1^2=1/2*m*Vo^2- F*T1

where v1 is the speed at which it emerges.

Here's Nathan Okun's summary of penetration formulae, it may or may not agree with the ghastly approach. http://www.combinedfleet.com/formula.htm
 
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This is why spall liners exist. Even if the bullet doesn't make it through a sufficient transfer of kinetic energy to the fragments of the armor on the other side can make people very unhappy. Almost certainly the round will no longer be shaped like a round after getting that far so there is no sense to the question of how fast whatever portion of the original mass might be going when much of the armor might have picked up speed.
 
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Years ago I saw an old automotive flywheel attacked with a Colt .45. None of the bullets went through but a lot of daylight did show through.
 
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AR500 might not be as tough as the equation implies
 
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I thought they invented kevlar for it's ballistic properties ?
 
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rb1957 said:
I thought they invented kevlar for it's ballistic properties ?
Click to expand...
IRstuff said:
Kevlar's original use was to replace steel belts in tires. As balistic protection against AP rounds, it might not be that effective, although it would be much lighter that AR500 steel

https://www.sciencedirect.com/science/article/pii/S2214914718301727
Click to expand...

Kevlar is still used for pistol rated armor (2A & 3A) but against high velocity, pointed rounds you have to use steel, ceramic, or new to the market is UHMW. It would take a lot of kevlar to stop 5.56/5.45/7.62, hitting it with an AP 50 BMG would be laughable.
 
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harrytos23 said:
Hi there!

I am trying to calculate how thick it needs to stop a 50 BMG AP caliber using AR500 plate. I used the formula that DoD published and I was able to get that it needs 0.554" plate to fully stop it.
View attachment 9796
My question now is, since we're using only 1 plate of 0.50" thk of ar500, in theory the bullet will go through the plate. I am wondering if there's an accurate way to calculate the velocity after passing through the first plate.
Click to expand...
I guessing this would be more practical for a vehical
 
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AR500 seems to be sold primarily as body armor material; vehicle armor is often something like RHA steel or Ti-6Al-4V.

I suggest OP search for the military standards for armor, which usually include some penetration estimates; of note is MIL-A-12560, which shows required thickness of 0.885 inches for 0.50AP M2 round at 2500 m/s V_50 at 0-degree obliquity


12560.png
 
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IRstuff said:
AR500 seems to be sold primarily as body armor material; vehicle armor is often something like RHA steel or Ti-6Al-4V.

I suggest OP search for the military standards for armor, which usually include some penetration estimates; of note is MIL-A-12560, which shows required thickness of 0.885 inches for 0.50AP M2 round at 2500 m/s V_50 at 0-degree obliquity


View attachment 9922
Click to expand...
Good point. Buy Kevlar I imagine is preferable.
 
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mfgenggear said:
Good point. Buy Kevlar I imagine is preferable.
Click to expand...
Actually, without some other material supporting the Kevlar, it's not going to be very effective against an AP round; see https://natshoot.s3.amazonaws.com/u...018/Stopforth kevlar 9mm projectlies 2018.pdf

Also, a 1994 ARL paper suggests that even 38.1-mm Kevlar WITH 12.7-mm aluminum facing can barely reduce a standard NATO round's velocity by 60%, so stopping an AP round would be nigh impossible with those parameters.
 
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