Tag Archives: M855

M855A1 EPR: The Armor Piercing Round That Wasn’t

The Army does not actually consider M855A1 to be armor piercing ammunition, but it is capable of some really impressive penetration. Standard M855 is stopped easily by ¼” AR500 level III body armor, but M855A1 can penetrate even level III+ steel armor.

Bear in mind that the plate in that test was able to stop 5.56mm M193 and 50 gr TSX, .450 Marlin 405 gr JSP, and even a round of 7.62x51mm M61 AP. This plate is seriously tough.

Let that sink in a bit: a standard 5.56mm “ball” round was able to penetrate a target that 7.62x51mm armor piercing ammunition could not get through. Of course the old farts will complain about how their beloved “thuty cal” will carry more energy down range and that is absolutely correct. 7.62x51mm will likely be better at getting through thicker, heavier obstacles like trees and possibly better at multiple layers of light barrier like car bodies. It will definitely be better at chewing up concrete barriers with multiple rounds. Still, at close range, in this narrow use case, a 5.56mm “ball” cartridge outperformed 7.62x51mm AP and that is really saying something. How far away does M855A1 EPR keep that performance edge though?

It is not particularly surprising that it loses some steam and is unable to penetrate at 50 meters, given the light weight of the projectile, but the fact that it can still get through the plate at 25 meters is notable in its own right. There is some limit to the capability of this new round, but it is nevertheless impressive. It is not simply some icepick penetrator, either.

Even when fired from a short barrel, M855A1 shows immediate upset and dramatic tissue disruption. In comparison, M855 shows a much longer “neck,” about four to five inches, actually. The “neck” is the portion of tissue that is relatively undamaged by a projectile’s passing before the bullet begins to yaw, fragment, or expand.

Even when fired from a 16” barrel, the M855 showed a longer neck and less tissue disruption than the M855A1 did from an 11.5” barrel. In other words, the M855A1 is more terminally effective at a lower velocity than M855. There is every reason to believe that it should continue to demonstrate excellent down range performance too, based on the light, three part construction of the bullet. It is refreshing to finally see an effective loading fielded for our soldiers’ 5.56mm rifles. For decades, civilians have enjoyed high performance loads that take full advantage of the 5.56mm cartridge’s potential but our service men and women have made do with an obsolete answer to a question no one cared to ask. The M855 was not particularly good at anything. It was not terrible, of course, but it was far from ideal. At long last, it looks as though the Army has a load that is actually better at penetrating cover than M855 but also produces better tissue damage.

Testing the 5.56mm MK318 MOD 0 / 5.56 SOST ammo

The 5.56 SOST  is the ammo currently being used by the USMC and other troops in the GWOT,  it has not been available for the public to buy for very long so I, like a lot of other people have been curious about how it performs. The round was designed to  have better terminal performance and accuracy from short barreled rifles with a muzzle velocity of 2925 fps from the 14.5 inch M4 barrel.  The round is a OTM,  this is important to remember as it is not the same as a hollow point.  It does however, offer up better performance and is barrier blind. The bullet itself has a thick copper base and a lead front end with the usual open tip that results from the process of making the bullet.  Also present are the rings seen around the bullet much like a barnes triple shock X.  A lot of people assumed and still do that the SOST is a barnes solid copper TSX, but it is not.

After getting my hands on some of the ammo I decided to test it for accuracy first. Since the ammo is intended for combat weapons, I chose to use my Colt 6940  with milspec barrel with 1/7 twist. I did put a Leupold 18x target scope on the carbine though so i could get all the accuracy out of it I could.  I fired 2 strings of 5 shots at 1 inch dots and one string of 10 shots of M855 to compare it to the common military load all at 100 yards. It was around 1100 AM , sunny with a  2 oclock 18 MPH wind.

Other then the normal 1st round flyer you usually get from hand cycling the action as opposed to letting the recoil operate and chamber  the next few rounds, the ammo showed some  great potential. The group on the left  was a little worse due to my own bad trigger work and lost concentration on one shot, but still pretty good considering. Now I know some claim  5 shot groups tell nothing, but if you over lay to  strings you get a pretty good idea  and you keep barrel heat down and mirage off the barrel messing with the scope.

After shooting the groups I decided to test out how the round matched the trajectory of the M855 since that is one of the things the SOST round was meant to have in common with the green tip. Out to 300and 400 yards  the SOST did match the BDC of my TA31F  ACOG and zero of other scopes and Aimpoint RDS I had on hand zeroed for the green tip. Also when comparing the position of the groups in relation to the aiming points, you can see on paper that the zero held very close for both rounds.

Now, the real surprise for me, was how good the lot of M855 I shot turned out to be!  Many gun board expurts and gun magazine expurtitions will gladly tell you how terrible green tip is in the accuracy department along with its many other flaws , makes it  slightly more useful then tits on a boar hog. After getting the carbine hot  after some drills using the SOST and playing around, I fired off 10 rounds fairly quickly  with the Colt/18x combo.  The results left me a little surprised, rarely have I seen green tip shot for accuracy  with sand bags, a table and a target scope further then 50 yards. And I do not recall having seen any pictures of it doing as well in a true 100 distance group.  I shot the green tip with all seriousness and the same concentrated effort I did with the SOST and the results were pleasing and a little surprising to me.  I have never taken the green tip seriously  enough for my own needs in the accuracy department so this will indeed lead to more testing of the M855 if for no other reason  then to see if this was a fluke.

Now I do not mean to sound like I think green tip is crap, I have seen some  good performance out of it at longer ranges on coyote size targets and even man sized targets. But on the other hand, I have seen some terrible accuracy from it too. Of course lots and different MGGs have as much to do with it as anything, not to metion the different shoots and the quality or lack of  in the guns used.

Back to the SOST, I think its a pretty good round from what I can tell. It is not MK 262 or TAP 75 gr. But for general issue to everyone, it is an iprovement in my humble opinion.  I have not shot anything living with it yet, but I will. Also, in the next few weeks I will test it though a few “barriers” like auto glass, wood, and wall paneling. Hopefully I will get to shoot through some auto doors as well.  I would not use it in my own house if over shooting is a issue, but I would use it for anything else at this point if you can find enough for SHTF bulk storing. And you have the benefit of practicing/training with M855 and still being able to shoot the SOST without a zero change. At this point I can not say it is better then any MK 262 top load in accuracy, but it is not meant to be, but, it is better then M193 by a long ways and it shows the ability to shoot a lot better the M855 and even if it just matches it in accuracy you still have the benefits of better terminal performance and barrier penetration while still holding together to hit the target behind if power point presentations can be believed. Hopefully my future testing will offer at least a tiny sample to help prove or disprove the new round.