(my first question - oh boy!)
I tried looking this up on the net, I really did, but the people offering answers are either pro- or anti-gun lobbyists so their views are a little biased. I’m really just curious from a material science / engineering perspective (I’ve got opinions on guns, sure, but I’m not hellbent one way or another). I’m just hoping I can get the answer sans any axe-grinding. So here goes -
The two main characteristics of armor-piercing bullets are 1) they’re made of a hard metal like steel instead of a soft metal like lead. 2) They are coated with Teflon or some other dry lubricant.
The reason for using a hard metal is pretty much accepted - the bullet will deform less on impact and can more readily pierce the armor. It’s weather the Teflon coating does any good that’s the thorny question.
One school of thought says it does help with penetrating the armor. The lubricant helps the bullet cleve through the material. A rough analogy would be if you were trying to pound a steel wedge into a block of wood with a hammer, you could try putting grease all over it to reduce the friction on its sides as it pushes into the material (I could see all kinds of practical reasons why you wouldn’t want to grease a wedge like that, but you get the idea.)
Piffle, says the other school of thought - the Teflon has no effect on the armor. The only reason you need Teflon is to provide protection to the gun itself from being damaged by the hard metal used by armor-piercing rounds. The hard metal tends to strip the rifling on the inside of the gun’s barrel, which doesn’t happen with normal soft-metal bullets. Indeed, the Teflon can actually reduce the bullet’s ability to penetrate armor. One example I read was that when used on soft body armor the Teflon can become entangled with the Kevlar fabric (offhand that doesn’t sound right to me, but I appreciate the fact we’re talking about something impacting something else at several times the speed of sound, so the law of physics could be acting squirelly here).
So can anybody point me to some unbiased research studies on this stuff?