Window glass? Auto glass? Lexan?

Does it start fragmenting immediately after impact?

Did a search here and Old Painless' site. Curious.

.223 doesn't so well through glass at all. I dont know about fragmenting though.

Any rounds that do go through glass well besides 50BMG?

I used to have a pic on my website of a DC-9 center cockpit window that was shot with a Tromix 50AE and the bullet blew the crap out of it.  Punched all the way through.  I also shot one with a 440 CorBon and a .458 SOCOM with the same results.  The glass is 2.5" thick of three plys of laminated glass.

Hit with a .223, it just takes a little chip out of the glass surface like it was hit with a BB gun.  That was with a 55gr FMJ bullet.  Maybe a 70+ grainer would fare a bit better, but I doubt by much.

A .223 against thick glass is horribly shitty............sorry.  ;-(

Lexan is polycarbonate and is like a soft pliable transparent plastic.  It works best laminated to the back side of glass to keep glass shards from blowing out the back side.  The glass absorbs the energy and the polycarb keeps the little pieces from blowing out the back.  Alone, Lexan will get punched through, no problem.

Autoglass is pretty thin, so if it isn't hit at an extreme angle, a .223 will probably go through without a problem, though I have not tested it.

Tony Rumore
Tromix Corp

Thanks Tromix.

www.tromix.com/Tromix_50AE.htm = got wood

I've heard of, read, and participated in a few tests over the years. Too many variables - type of round fired, angle of impact, type of glass, etc. - to provide a simple answer.

In my own experience, 5.56 rounds do frequently fragment and even when remaining intact frequently deviate considerably from the original trajectory.

FWIW

If you go to LE.ATK.com, click on the federal tab, and then the ".223 rifle data" box it has the results of federal loads through various barriers. Page 7 is auto glass. even after penetration of the glass many of the loads had unacceptable penetration into subsequent ballistic gel. I was told the local PD is using the 55 grain soft point TRU load. The load shows 2.25" gel penetration after the glass, not much good IMHO. Interesting data if you have not seen it before.

Am I wrong to think that the first or second shot at auto glass may not fare well but subsequent shots through the shattered safety glass will have more energy?

Looks like it did good here.

Just for gigles, took some 707 laminated passenger windows to the range. 55gr FMJ at range of 200 meters, each shot seemed to do something different, from shattering it with no penetration, to nice neat .22 holes drilled through and through. Wish I had a camera with me.. But as a previous poster stated, too many variables it would seem..

i read somewhere that the FBI (i believe) uses the Federal trophy bonded bear claw for shooting through auto and store front glass because it tracked the best after penetrating through the glass.

64gr trophy bonded bear claw

Well in my experience with auto glass the first 2-3 shots shattered the glass but did not penetrate the windshield.  Multiple hits to the same area after the first 2-3 rounds will go through.  As for side and rear windows they either shattered on the first or second shot.  The rear window first shot the back window blew out.  This was done on my buddy's 1985 GMC Jimmy that had completely died and was destined for the wrecking yard.  So we decided to shoot the shit out of it before he trailered it of to the wrecking yard.  We turned that thing into swiss cheese.  The GMC Jimmy rear windows were notorious for shattering though, you could shatter them by closing them to hard.  I wish I had pics.  I think my buddy may have some saved somewhere.  If he can locate them I will post them.

ETA: Forgot to mention we were using 55gr ammo of various manufacture.

5.56/223 ammunition does not fair well against glass.  With the right round and variables penetration is possible, but not reliable.  In a pinch I would not hesitate to engage an appropriate target behind glass with a 223 if that is all that is available.  If glass is a known barrier then plan ahead take something else.  

I believe one of the better known rounds for glass penetration is the 62 gr. Federal Tactical ammunition.  

Good luck,

Mike

The heavier projectiles do much better, as do the ones with steel penetrators. Hornady 77gr TMJ would be my choice if I had to hit a mark behind glass, although 5.56mm would not be my first choice for this purpose.