Army And Marine Corps On M855 Ammunition
BY Herschel SmithBut the Marine Corps and the Army’s decision to use two separate types of 5.56mm ammo is not a simple oversight.
The Army adopted the M855A1 in 2010 after years of struggling to find a lead-free replacement for the Cold-War era M855.
In recent years, troops also criticized the M855, saying it often delivered ineffective results on enemy behind battlefield barriers such as car windshields.
The M855A1 features a steel penetrator on top of a solid copper slug, making it is more dependable than the current M855, Army officials have maintained. It delivers consistent performance at all distances and performed better than the current-issue 7.62mm round against hardened steel targets in testing. It penetrated 3/8s-inch-thick steel at ranges approaching 400 meters, tripling the performance of the M855, Army officials said.
The Corps had planned to field the Army’s M855A1 until the program suffered a major setback in August 2009, when testing revealed that some of the bullets did not follow their trajectory or intended flight path.
The earlier design of the M855A1 featured a bismuth-tin slug which proved to be sensitive to heat, prompting Marine officials to stick with the M855 and also the Special Operations Science and Technology round developed by U.S. Special Operations Command instead.
Commonly known as SOST ammo, the bullet isn’t environmentally friendly, but it offered the Corps a more effective bullet, Marine officials have said.
I confess that until this article I didn’t know that the Army and Marine Corps were using two different types of ammunition. If I’m not mistaken, the SOST is an open tip bullet with a lead core and copper shank. It expands much like a hollow point should.
Saying that the better penetrating capability of the M855A1 through car windshields was the reason for transition from M855 to the M855A1 (with copper slug instead of lead) is like a recapitulation of the reasons for transitioning from the FMJ lead ball to the M855 in the first place. It’s more likely that environmental concerns caused the Army to transition to the M855A1. I cannot think of a worse excuse.
I will also remark that when I learned of the copper slug in place of the lead ball for M855A1 my thoughts immediately went to barrel wear and loss of rifling. It appears that this is in fact a legitimate concern.
So in summary, the SOST is much like the .223 pointed soft point for game hunting, except that it has a copper shank. If a reader would like to weigh in on the effects of the copper shank, please do so (in an educated fashion – and do not allow this to become yet another worthless argument over 7.62 v. 5.56).
Finally, don’t forget the main reason for the lethality of the 5.56 mm round, which is the fact that it is frangible and immediately fractures into pieces leaving multiple tracks through ballistics gelatin. See the excellent paper Small Caliber Lethality: 5.56 mm Performance In Close Quarters Battle. It appears that the Army has forgotten the simple things.