Army And Marine Corps On M855 Ammunition

BY Herschel Smith
8 years, 11 months ago

But 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.


  1. On March 23, 2015 at 11:23 pm, 45B20 said:

    I’ve said it loud and proud for decades; when something absolutely must be dropped on the spot a 22 is not the go to caliber

  2. On March 27, 2015 at 12:41 am, mcian said:

    Place it in the right spot and it works quite well.

  3. On March 24, 2015 at 7:06 am, McThag said:

    It’s a copper core and a gilding metal jacket with an exposed steel tip. The same gilding metal used on pretty much every “copper jacketed” round. The jacket composition isn’t the reason for accelerated barrel wear, it’s that M855A1 is loaded hotter.

    The way the round is made, it should yaw and fragment at lower velocities than M855 did, which means it’s effective farther out; being lead free is a ploy to sop up some enviro-weenie bucks to help develop the new round.

    All they really need to do is get quality control in place to fix the trajectory thing…

  4. On March 24, 2015 at 9:16 am, Herschel Smith said:

    ” … being lead free is a ploy to sop up some enviro-weenie bucks to help develop the new round,” and “All they really need to do is get quality control in place to fix the trajectory thing…”

    Uh huh. QC, and environmental issues. I can see the USMC using both of these as good excuses NOT to be involved in the round. As to the issue of the jacket metal being responsible for barrel wear, I wasn’t implying that. I would think the hardness of the metal (compared to lead) would have been more responsible. After all, the core has to deform a little bit in order for rifling to work.

  5. On March 24, 2015 at 10:24 am, Lina Inverse said:

    Unless the cannelure is right at the steel to copper slug juncture, I don’t see the described bullet breaking into 2 pieces at all, and I don’t see the bottom half fracturing at all. So likely better barrier penetration, with vastly less performance on human targets.

  6. On June 2, 2015 at 4:33 am, Delphi said:

    I have found a recent gel test.

    I would say it fragments very well.

  7. On March 24, 2015 at 10:01 am, Ned Weatherby said:

    The 885A1 round operates at a much higher pressure than standard ball ammo. I wonder how that’s going to effect the AR platform in the long run? I haven’t heard of any military service utilizing heavier buffers or stronger springs to slow down the bolt carrier from the higher pressures.

  8. On March 24, 2015 at 10:51 am, Lina Inverse said:

    Open tip is very much not the same as soft point, which we don’t allow ourselves to use. It’s much more a manufacturing technique, used for target and sniper bullets like the Sierra MatchKing, because variability at a small tip is much less significant than at the large base.

    Based on pictures of the Mk 318 SOST, the jacket over the lead tip is drawn from the copper shank up and over the lead tip. I’m sure this is officially done to save costs, and is not intentionally designed to cause greater damage to humans … but the width of the open tip is way more than than any open tip bullet I’ve seen. I bet it would be outlawed sooner or later by the usual anti-military types or bed-wetting squishes who are also officially on our side, if anyone were to try to widely field it, so it doesn’t strike me as a real solution prior “to the revolution”.

    I really want to see results from calibrated ballistic gelatin, but this picture, for example, is very encouraging. Fragmentation of the tip’s jacket, although I wouldn’t expect that to pass through a barrier, and the lead in the bullet expands significantly, given the very small diameter that it starts at, but not dramatically like soft point bullets. Could be superior in every way but not being completely Green.

  9. On March 24, 2015 at 11:00 am, Herschel Smith said:

    Good research sir. It keeps me from having to do it. I like it when commenters are the writers and editors for the site.

  10. On March 24, 2015 at 1:35 pm, Lina Inverse said:

    You’re welcome.

    I spent some more time, and couldn’t find a single gelatin test of M885A1 except one after it hit a steel barrier, after which the steel tip detached from the copper rear. Even given the limited availability of this round outside of the military (no doubt due to its very high pressure, I can’t see Federal selling these or my putting them in my own rifle), I think the absence is telling, and I am not reassured by the bald assertions that it’s better than M885 on humans. Especially given the near total corruption of the military/Army establishment in this area since the ’50s.

    On the other hand, I found an informal test, with perhaps an attempt at calibration, of Mk 318 here, which looks good.

  11. On May 16, 2015 at 2:43 am, majorrod said:

    The Army is keeping a very close hold on the soft tissue performance of M855A1. The closest civilian competitor from which is was derived is Liberty Ammunition’s T3. There’s a lot of video out there of it being used against ballistic gelatin with outstanding results.

  12. On March 24, 2015 at 11:33 am, Pat Hines said:

    There has been some SOST for sale.,rrsrkqbqqrwwwqwxsrfddtdgbdk,vi/stkgrdksfxsqwfqqbdqxkrrffsdss/5/41655/8298317/5_56SOST-vi.jpg

  13. On March 24, 2015 at 12:36 pm, Ned Weatherby said:

    Correct. It has been available from time to time, in 5.56 and 7.62. I think the 7.62 SOST is a 130 gr top. But the 855A1 is only for the “special people.”

  14. On March 24, 2015 at 1:37 pm, Lina Inverse said:

    I think you have to be very special to want to put that high a pressure round in anything other than something like a very strong bolt action rifle! I can’t see Federal selling seconds or canceled orders of this like they do with M193 and regular M885.

  15. On March 24, 2015 at 8:08 pm, Ned Weatherby said:

    So right. Funny how the Marines quickly adopted a standard pressure round (SOST) that works well for barrier penetration, yet retained standard SAAMI chamber pressures. And I agree – the Federal SOST fodder I’ve seen for sale isn’t like firing proof loads in your rifle. It’s likely that the 885A1 ammo uses temperature stable powder, and may be, for the most part, safe to shoot without grenading one’s rifle. But I wouldn’t bet on anything with the new “green” round. The Army had problems with the 5.56 A1 EPR when first introduced in the sand box, and recalled a bunch of it.
    If they wanted to make a 5.56 “light magnum” round, they should have subcontracted the task to Hornady. They’d have saved the 32 million bux in R&D in early 2012 ,and probably had a round that worked the first time – although it might not have been “green.” (Don’t they know about paint for the “green”? Heh.) However, the 32 million in R&D appears to include a rip-off (in typical government fashion) of an existing 5.56 top:
    So add another 15 million to the initial R&D cost – and a royalty on all produced rounds- if the Army’s likely appeal fails.

    The whole “green” thing is, IMO, bullshit. Ground troops are often following aircraft and accompany tanks that use depleted uranium rounds. Other penetrators, like tungsten carbide, are also potentially toxic when the dust is inhaled, as is the dust from DU.

    Anyone who is, or has been, in the military, know any health problems associated with munitions or chemicals, will get the runaround from the VA, so I maintain the “green” boolsheet is an idiotic PR stunt. “We are here to blow shit up and kill you, but we won’t leave a footprint that isn’t approved by the Green Party.” Gimme a break.

    The fact that they are using a faster burning powder is, of course, going to raise pressure, unless the load is tailored properly. And of course a faster burning propellant is going to reduce muzzle signature. As you know, slower burning powders typically produce faster velocities at lower pressures. It’s just the part about getting 20″ barrel velocities out of a 14.5″ barrel that’s the problem. I’d bet Hornady could do it, as they have with their “Light Magnum” loads, although their proprietary powder blending and drop system is, as far as I know, still secret from the Army spies.

    Oh crap, Lima, there I go again…

  16. On May 17, 2015 at 2:20 am, majorrod said:

    “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.”

    You are misinformed. I strongly suggest you read “In Search of Lethality: Green Ammo and the M855A1 Enhanced Performance Round” by MAJ Glenn Dean who has first hand knowledge of the issue. The Army has been kicking around a “green round” (no lead) for almost two decades. Concur it’s pretty silly but in training areas near civilian populations and in certain parts of the country lead leaching into the environment is a real issue the Army can’t ignore at the risk of stopping training (remember a certain red woodpecker at Bragg…)

    That said M855A1 was born from the funds that were available for a “green round” AND the real world realization in ’05 that we need a better round than M855. A conscious decision was made to not emphasize we want to find a round to kill people better and a desire to pursue ALL types of solutions including some that would have raised the concerns of “legal chickens”. Publicizing those goals would have potentially have created obstacles or slowed the program further than it had already suffered by all the good idea fairies especially those concerned that we not cause too much pain to our enemies when we kill them.

    So in short around ’05 a savvy decision recognizing the PC climate we live in was made to use money already obligated to find a more lethal round instead of starting from scratch. The fact it had to be green kept the money tap open but wasn’t the focus.

    I’ll be publishing an in depth essay on M855A1 & Mk318 Mod 0 on my blog Gruntsandco in the next couple of days.

  17. On May 18, 2015 at 6:46 pm, Herschel Smith said:

    Whatever. You can say what you will. I don’t think I’m misinformed at all. The current round does fine, and it is built the way it is for a reason. And the USMC doesn’t want to use the Army round for a reason.

  18. On May 18, 2015 at 9:11 pm, majorrod said:

    I wasn’t trying to insult you when I said you were uninformed about an issue. No one can know everything. I’m constantly learning and appreciate (sometimes grudgingly) when I learn things I did not know and accordingly change my position if warranted.

    I see what you did though. When someone offers you information that supports your preconceived notions like “lime inverse” above it’s “good research”. (BTW great info) When the facts don’t get you the conclusion you want it’s “say what you will”. (You may want to re-evaluate the portion I quted from your essay and look up the definition of speculation or opinion also known as “say what you will”.)

    Mk318 is a good round and does well, just like M193 and M855 did before it. Does that mean the Corps should have kept on using M193? Should we stop improving or only stop improving when it’s the Army that makes the advancement?

    The reasons the Corps selected Mk318 are well known. It wanted better performance against individuals and wanted something that would reliably penetrate windshields on VBIED’s. The Corps also continues to stock & use M855 because of its penetration subtly acknowledging a weakness in Mk318. M855A1 does what Mk318 does AND exceeds M855 performance.

    You don’t seem to know the USMC is testing M855A1. Don’t be sure the USMC doesn’t want the round. No need to respond. I won’t post further since it’s not facts you want, just agreement.

  19. On May 19, 2015 at 9:00 am, Herschel Smith said:

    “No need to respond. I won’t post further since it’s not facts you want, just agreement.”

    Yea, like leaving your comment instead of just deleting it which would be easiest if all I wanted was agreement and accolades.

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This article is filed under the category(s) Ammunition,AR-15s,Guns and was published March 23rd, 2015 by Herschel Smith.

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