Many articles have been written about M855A1 since the US Army first announced plans to adopt a new “green” 5.56x45mm cartridge to replace M855. Often, those articles have been highly speculative or have referenced results from earlier versions of the M855A1 cartridge, before it was fielded widely. There has been a reflexive tendency to look poorly on the new cartridge because of its supposedly environmentally friendly design. It is popular to denigrate anything labeled “green” as being inferior to the original flavor, non-filter, leaded, trans fat version, but that is not always accurate. “Electric car” sounds like some sort of weak, hippie nonsense, but a Tesla Model S can do 0-60 mph in 2.8 seconds. As the ammunition filters out into the public, and independent testers get hold of it, some remarkable results are coming to light.
This test used a chrome lined, 14.5”, 1:7” twist barrel to match the M4 barrel that this round will be fired through most commonly in combat. The most immediately apparent result is the almost complete absence of a neck. Typically, when a projectile enters tissue, it travels some distance before it begins to yaw, expand, or fragment. This leaves a relatively narrow wound channel visible in the gel before the upset begins and this narrow portion is referred to as the “neck”. M855 is notorious for having erratic performance in this regard, with the neck sometimes being somewhat reasonable (4”-5”) and sometimes being so long that the projectile is likely to exit a target before beginning to upset. This erratic performance is due to a variety of factors including muzzle velocity and in-flight projectile yaw, but the end result is that it can sometimes produce the ice pick wounds that we often hear of anecdotally. The extremely short neck exhibited by M855A1 in this test is very encouraging in that it seems to indicate M855A1 is more able to reliably produce incapacitating wounds than M855.
The question that remains is how M855A1 performs out of short barrels or at longer range. Does it continue to produce an extremely short neck at lower velocity?
The answer appears to be “yes”. It retains the practically nonexistent neck seen in the longer barrel test. This gives us a peek into what the performance could be at about 100 yards. It is important to remember that it is a sample size of one, so it is by no means conclusive. It does present a rough idea of what we could expect, though. As mentioned above, M855 can perform adequately at close range, but as distance increases and velocity decreases, fragmentation occurs deeper in the target, if at all. As velocity decreases beyond 2,700 fps or so, fragmentation may not occur at all. The fact that M855A1 was able to fragment almost instantly, even when fired from a short barrel is very encouraging.
As good as the performance in tissue looks, it is irrelevant if the projectile cannot even make it to the tissue because of intervening obstacles. M855 was adopted in part for its ability to penetrate Warsaw Pact steel helmets at 800 meters. M193, which was replaced by M855 can penetrate level III steel body armor, when fired from a 20” barrel at 50 feet or less, due to its relatively high velocity. M855 typically cannot penetrate that same armor. M855A1 has an exposed steel penetrator that is pointier and about twice the weight of M855’s penetrator, so it looks as though it was designed with penetration in mind, but how does it actually perform?
The test does show that M855A1 can penetrate steel armor, but it isn’t quite that simple. The armor used in this test is not just level III, but an improved version the manufacturer refers to as level III+. The plate used in the test stopped M193 in a previous test so M855A1 is seen here penetrating a plate that neither M855 nor M193 could penetrate. This does not mean that this armor is inferior in any way, it simply means that M855A1 is significantly better at penetrating hard barriers than its predecessor.
M855A1 might be considered “green” because of its lead free design, but it appears to be a dramatic performance improvement over M855. Rather than compromise performance for the sake of environmentalism, as some critics have claimed, it seems very likely that the Army used the political desire for environmentally friendly ammunition to develop and field a more effective replacement for M855. Time will tell, but it appears that American soldiers finally have a better small arms cartridge.