M855A1 is the Army's new "green" ammunition. It's NATO spec and replaces the old lead core with steel penetrator M855.
The M855's copper jacket comepletely encases the steel portion and there's a lead plug behind that.
Pic sourced from here.
The new M855A1 round has no lead and the steel part is exposed at the tip.
Pic sourced from here.
Look Ma! No lead! Same 62gr bullet weight, slightly longer projectile. Lots and lots of information touting its superior performance in penetrating armor and barriers. It can penetrate a 3/8" steel plate at 300m where the old M855 and 7.62x51mm M80 cannot! What I am not seeing is how it performs in people. The entire point of an infantry round is killing people after all.
This might be another example of the non-emotional approach GURPS took to ammunition performance may be prescient. M855A1 behaves very much like AP. AP ammo gets to divide the DR by 2, but it will also be one stage less wounding. Ball is pi, AP of the same type is pi- after penetration. Or half damage.
It's a means of saying that an AP round will make a nice .22 caliber hole without expanding. This is a problem that M855 has as well. Especially in very thin people where the fragmentation that 5.56 is famous for occurs just behind them.
The more I learn about wound ballistics the more convinced I become that the old fashioned M193 was the best 5.56 round we issued in terms of tissue damage and NATO's chasing the ability for the 5.56 round to penetrate body armor and light barriers has compromised its ability to perform its primary function, stop bad-guys.
The 5.56's ability to penetrate armor was basically to convince NATO members to drop their 7.62x51mm guns and change over to the new 5.56x45mm. Recall that SS109 (which M855 is) was developed by FN-Herstal; and who benefits most from an army changing to a new rifle? Gee, could it be a gun maker? Pity the FNC didn't take off, huh? Gang oft aglave.
This also wouldn't have been an issue for NATO if we 'Mercans hadn't bailed on the entire idea of a 7.62x51mm service rifle. Yeah, that made NATO happy. You may recall that NATO was considering the German 7.92x33 Kurz and .280 British when we declared that we'd not accept a round that wasn't identical to .30-06 in performance. Hell, M59 (7.62x51mm) ball uses the same bullet as M2 (.30-06)! Then just a couple of years after shoving our pet round down their throats we chuck it in the waste basket.
What nobody doubts is that 7.62x51mm is effective at distances, effective against barriers and is lethal. It is also much heavier than 5.56x45mm and so are the guns that fire it. Note my FAL and it's 10.4 lb. tare compared to a 14.5" barreled AR at 6.6 lbs. 20 rounds of FAL ammo in its magazine is 1.7 lbs. compared to 30 rounds for an AR for 1 lb. That's hard to work around.
This is why I am a proponent of 6.8x43mm. Due to the mass of the bullet, it's better on barriers than 5.56. Hogs and deer make a good stand in for people, and 6.8 is snuffing them and how. The weapons are the same mass as a 5.56 gun, the draw back is the ammo weighs more; 1.7 lb. for 30 rounds in an AR type magazine. For a typical combat load we've added almost five pounds to our poor grunt.
But we gain a lot. By the way, most any argument for 6.8 will also work for 6.5 Grendel. In the long run though, 6.8 would be better once we started talking about needing belt fed guns. The case design comes into play here.
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