Reprinted from Small Arms Solutions and authored by AR-15 expert, Chris Bartocci. -NCS
A Great Round “If” We Had a Rifle Designed to Shoot It!
We have discussed doing a video on the M855A1 cartridge for quite some time. Looking over all the information it seemed to make more sense to do it in a blog article where it could be articulated better. There are several issues with the new M855A1, none of which are based on the performance of the ammunition. Problems are caused by the pressure it is loaded in and the projectile type, which significantly decreases bolt and barrel life of any firearm it is put into.
Shown above is a comparison of the M855, M856 Tracer, early M855A1 and the issue M855A1. The difference between the early and issue M855A1 projectile is the plug under the penetrator. Early projectiles used a tin/bismuth alloy. It was found there was not enough mass to it to properly stabilize in the arctic environment so they switched over to copper. Lead has more mass to it than either the tin/bismuth or copper alloy for the same weight. You have to have more copper to get the same weight. You will notice that the M855A1 projectile is just slightly longer.
Looking at the cross sections you are able to see that both projectiles are made up of three components. The M855 (left) consists of a copper jacket, steel penetrator core and lead plug. The M855A1 (right) is manufactured from a copper jacket, steel arrow head core with a copper plug. The M855A1 projectile fit the Army requirement for a “green” projectile that does not have any lead. This creates a much more expensive projectile. How was the Army able to sell this more expensive projectile? They increased the cost to produce all other military rounds to offset the expense of this new cartridge.
Shown is a US Government comparison chart showing the M855 on the left and the M855A1 on the right. Notice the vital information left out, velocity and chamber pressure. This information is where the metal meets the meat. This is the area that is significantly different between the two that has caused all the controversy. I have seen government spec sheets that include their claim the M855A1 is many steps ahead of the M855. However, I have never been naive enough believe the government gives all the proper info out. Like most things, I never pay attention to what others tell me so I find out for myself. I took M193, M855, M995 and M855A1 to a ballistic laboratory and got all the information. Regardless of what the Army claims, this is an independent test.
Armor Penetration
I procured a 1/2 piece of armor plate. The steel was secured to a railroad tie so it was stationary and would not move. The rifle was a 16 inch M4-type rifle and each shot was taken at 25 yards. One round each of M193, M855, M995 AP and M855A1 were shot.
Looking at the top left is the M193 Ball (FMJ). You can clearly see not much more than a dent. To its right is the M855, only slightly better and you can easily see the slightly deeper penetration due to the steel penetrator. Bottom left is the M855A1. Clearly the M855A1 is superior in hard steel penetration going approximately half way through the armor plate. To that right is the M995 Armor Piercing round which completely penetrated the steel.
Terminal Ballistics
The Army claims that the M855A1 round is superior in terminal performance. They claim that the M855A1 is not yaw dependent. This part of the testing did not necessarily show the new round to be a better terminal performer than the M855.
M855
M855A1
Clearly the tissue damage was better with the M855. The biggest difference was the Initial Yaw began at 1.25 inches on the M855 and the M855A1 started earlier at 1 inch. The M855A1 completely fragmented, retained nothing. The M855 retained 48.2% of its weight. Now this type of gel is not an exact match for human tissue. It does not take into account the different density of various types of tissue/organs. It also does not take into account bones. I would be far more likely to say wounding tissue damage was closer to comparable.
Mechanical Issues With M4/M16-Series, as Well as Others
The biggest problem with the M855A1 ammunition is the way it is loaded. It is NOT loaded to the 5.56mm NATO specifications, which all 5.56x45mm caliber rifles are designed for. This is clearly in violation of the NATO standardization contracts. The Army has not been forthright to anyone, including our allies, to the extremely higher port and chamber pressures that will cause bolt breakage, damage to receiver extensions, upper receivers and cause a barrel to wear 50% faster. The M855A1 was designed to give 20″ barrel performance in a 14.4″ barrel. Part of this was a change in the propellant change which brought pressures higher to peak at the shorter carbine gas system rather than rifle length gas system.
As you saw in the government released info on the M855A1, they did not release muzzle velocity or chamber pressure. There had been many rumors going around as to what the specifications actually are. So to come up with undisputable facts of what all these numbers are, I tested in a ballistics laboratory both the M855 as well as the M855A1 for comparison purposes.
M855
M855A1
Looking at chamber pressure, both cartridges were fired in a 14.5 inch M4A1, both projectiles are a 62 grain projectile. The M855 has an average chamber pressure of 51,522 psi, which is within the 52-55,000 psi range the M4 and all 5.56mm military rifles are designed. The M855A1 is increased vastly to 61,830. In fact, you see pressure levels as high as 62,900 psi. Please keep in mind that a proof cartridge is 70,000 psi. Clearly the rifle is being significantly driven past its design parameters. The increase in chamber pressure also increases the bolt velocity substantially driving the cyclic rate much faster, which increases parts wear and service life of both the bolt and barrel.
Bolts have been known to break within 3,000 rounds and barrel life has been cut by 50%. This is NOT a deficiency in the M4 carbine. The first time the M855A1 ammunition was tested was not in M4/M16 rifles. It was conducted during the Individual Carbine completion, which not one of the entries stood up to the M855A1, and none completed the endurance testing. All of the entries were designed around the M855 ammunition and worked excellent and passed all the military testing internally at the manufacturers prior to military testing. The bottom line is that as good as this round may perform, neither the U.S. nor any of our allies have any rifles that will stand up to the high pressures of this round.
Feeding Problems
Due to the shape of the projectile, as well as the hardness, feeding the M855A1 through a standard GI magazine caused problems. The projectile was not introduced high enough to fully clear the feed ramps on the barrel extension causing the hard sharp tip of the projectile to damage both the upper receiver, as well as the feed ramps, and end of the barrel extension. This damage was done in just under 8,000 rounds of M855A1 usage.
To correct the feeding issue the Army developed a 4th generation Enhanced Performance Magazine (EPM). The purpose of this new magazine is to change the feed angle of the feed lips to introduce the tip of the cartridge higher so the tip of the cartridge would clear the feed ramps preventing this damage.
The tan magazine is the EPM and the grey magazine is the standard issue Gen 3 tan follower magazine. Notice how much higher the M855A1 sits than the M855 to give more of a direct feed into the chamber.
So, in other words, if you do not want to damage your feed ramps, barrel extension or upper receiver you have to use the EPM magazine identified by a blue follower and tan magazine body. On a positive note, when tested, the new PMag Gen 3 magazines that have been adopted by the Marines, is compatible with the M855A1 ammunition and does the same as the EPM for feeding.
Bolt Breakage
Due to the higher chamber and port pressure, the rate of fire has been significantly increased. The wear on the bolt is excessive, driven beyond the operating parameters from which it was designed. As many as 3,000 bolts have cracked in half. Few bolts have been known to last a 6,000 round endurance test. Of course, heavy round counts of fully automatic fire also can cause severe wear or premature wear.
During the Individual Carbine trial, many rifles experienced these same types of bolt failures. Locking lugs have also broken off. I do believe some of the enhanced bolts will last longer, but not significantly longer. This is again not a failure of the rifles, it is ammunition induced. The ammunition drastically exceeds the design parameters of the 5.56x45mm ammunition specifications.
Barrel and Suppressor Failures
Due to the speed and pressure the barrels have had a drastic loss of life. Many engineers I speak to say it is up to 50% loss in barrel life. Barrel life is a difficult thing to configure. There are many factors that go into barrel life, including full auto use, maintenance or lack thereof, corrosion or type of ammo used. The M855A1 is at least an additional 200+ feed per second over the M855/M193 ball ammunition that the 5.56mm cartridge was designed around. Fire cutting of the gas port is drastically increased, which with use, the cyclic rate increases even further.
That higher cyclic rate causes, as we said, bolt failure, as well as failures to extract due to the cartridge case having residual pressure at the moment of extraction. This results in the extractor sheering off the rim of the cartridge face, leaving the cartridge in the chamber, breaking of the extractor, as well as pre-mature wear of the extractor spring, adding to overall extraction failure. Failures have also been seen where gas leaks around the projectile causing short stroking of the action. Due to all the mentioned velocity issues, it has also been found that sound suppressors have a significantly shorter service life.
Claim the M855A1 Does Not Change M855 BZO
It was clear the exceptional accuracy of this M855A1 round was contrived. The excellent groups shown by the Army did not come out of standard M16A4 and M4 carbines, but match Army Marksmanship Unit rifles. My testing was done with a standard 14.5 inch M4 carbine with a Leupold optic. There was a 1.5 inch shift in point of impact from one M855 2 shot group to a M855A1 2 shot group. This would require a rezero in my opinion. This was a repeatable process, both grouped similar. The M855 average was 1.48 in and the M855 showed 1.30 in groups. Nothing proved to be earth shattering.
Other Branches Refuse to Adopt the M855A1
Other branches, in particular the Marines, have refused to adopt this new round, and justly so. First, the overly hot round will not function properly in their M27 HK Infantry Automatic Rifles. This is an over gassed design from the start. This additional pressure causes failures to extract and pre-mature parts breakage. In other words, the reliability of this platform has been vastly compromised. They are aware of the parts failure from this round and are not willing to subject their fleet of weapons to this. They have their own preferred load called the MK318 SOST round which is a barrier blind round. It has excellent penetration, as well as desirable ballistics that do not damage their weapons. This round has been in use by them in the Global War on Terrorism. It has drastic terminal improvement over the M855. The Corps still issue the M855 as well. The Air Force is continuing with M855 for the same reasons. The Navy has a plethora of special rounds procured by them. They will not use the M855A1. In my time in Afghanistan in 2011, I saw soldiers from all branches, and I asked them what they were using for rifle ammo, only Army personnel had the M855A1.
This leads us into congressional tension. They are quite upset that all the branches are using different rifle ammunition for the same weapons platform. When the military switched from M193 to M855, it was across the board. Not now. Investigations have gone into why the other branches refused. Clearly the ammunition is not suitable for any rifles in current production. Although there is an increase in penetration, is environmentally friendly, and appears to be more accurate, this ammunition is detrimental to any weapon it is put in. The nearly 50% decrease in service life, in my opinion, is unacceptable. The fact that this round is not compatible with our allies weapons is unacceptable. The higher cost of the ammo is unacceptable, even though the Army has increased the price of other ammunition to make the cost of the M855A1 look cheaper, is also unacceptable.
Conclusions
I see a very interesting parallel with the M855A1 story as to the IMR vs. Ball powder story of the Vietnam War. The rifle was designed for the IMR propellant, which gave a rate of fire around 800 rounds per minute. And it worked as intended. Now the Army switches to Ball propellant, causing the rifles rate of fire to increase to in excess of 1000 rounds a minute. This caused parts breakage, as well as failures to extract. The Army was warned against this, but knowingly moved forward. The intent was clear when Colt told the Army that the Ball propellant ammunition pressures were too high; the rifles could not meet the cyclic rate requirement, and the rifles shot too fast.
Rather than stop the use of ball propellant they told Colt to only use IMR loaded ammo for cyclic rate testing. Of course, once those rifles got to Vietnam, the soldiers were issued ammunition loaded with ball powder. Many died due to this decision and the Ichord Committee claimed the Army’s handling of the M16 rifle program was borderline “Criminal Negligence”. Now we have the Army pushing another round, which further increases pressure; designed with the knowledge of its problems caused to the weapon and issuing it anyway. Weapons are breaking and wearing prematurely, which is known by the Army, and is such a problem that none of the branches will use the ammo. It is drawing scary parallels to the M16 development in Vietnam. And that history has clearly taught the Army nothing.
I see this as a good round “if” we had a weapon to fire it. We don’t have such weapon. What little benefit it offers is not worth destroying an entire fleet of M16A2/A4 and M4 carbines used by the U.S. military, and the cost which will go into frequent barrel and bolt changes. The ammo is not worth the cost of having weapons fail in combat by either the troopers not having the proper magazine, or their bolts breaking, or their bullets keyholing, due to a worn out barrel in 3K short rounds. The better alternative is the M855, as it keeps the barrel serviceable to 10,000 rounds or more on a properly maintained rifle. It is a mistake having ammunition not compatible with our allies weapons. This could cause major problems if we had to resupply an ally in a bind and their weapons fail to function because they don’t have an EPM or a Gen3 Pmag; also when this ammo causes parts breakage in their firearms.
I see this as too risky for our troops to use with current 5.56mm weapons platforms. We have seen this before in Vietnam and we know the disastrous consequences that it can have on our troops. The Army has all this information and is blindly moving forward, while other branches are holding their hands up and saying “No way!”. I believe the MK318 SOST round is a much more viable alternative as a main service cartridge that gives all the benefits without compromising the integrity of the weapons that shoot them. I think the “green” lead free is a great theory but they need to do it with a proper cartridge that does not exceed specifications.
“The Army has not been forthright to anyone, including our allies, to the extremely higher port and chamber pressures that will cause bolt breakage, damage to receiver extensions, upper receivers and cause a barrel to wear 50% faster.”
…LOVELY!
and all this is for openers….mag feed issues…
Thanks for an honest eval, Chris and NC Scout.
DOD lied and Johnny died! Some things never ever change!
Chris did some good work here. His Small Arms Solutions channel/site is worth paying attention to especially for technical information about the AR15/M16 series of weapons.
The 62gr OTM that the Marines are using definitely seems better.
I have a huge amount of respect for him and I think he’s the foremost expert on the AR-15, alongside C.Reed Knight, in the world today.
Hard to find now but some years back the answer with M855A1 and M80A1 was pull the bullet and reload it? Also the damage to the feed ramp was after 8k rounds. I thought a lot of people start considering changing the barrel out around 5k rounds?
But if it is too risk for our troops send it my way then.
You could, but honestly its better off to just grab better ammo.
Am I misunderstanding your claim about “extremely higher port pressures” or the test results (18070 vs 18550, a decrease in port pressure)
Look at the chamber pressure- the chamber pressure of M855 is around 51,500, while the chamber pressure of the M855A1 is 61,800, which is over a 10,000 PSI increase. The port pressures on those tests do seem to be slightly lower for the M855A1, which combined with the higher chamber pressures probably means that the M855A1 is loaded with a faster burning powder, which is going to put more stress on bolts and barrels, and also increase the rate of throat erosion.
I reviewed the report in detail and I am very aware of the throat erosion due to chamber pressures, but port erosion and cyclic rate increases are not likely. Bolt failures are dubious as well.
My understanding is that the bolt failures are being corroborated by real world evidence. Increased chamber pressure, especially when it is an increase of approximately 20%, will certainly cause increased bolt failures. I mentioned throat erosion, not port erosion- increased throat erosion WILL happen with faster burning powders and increased pressures.
I am not arguing with you, but with the article: “Fire cutting of the gas port is drastically increased, which with use, the cyclic rate increases even further.”
1) there is no evidence presented to support higher port pressures — the opposite is instead shown
2) there is no evidence presented to support flame cutting of the port (faster powder means lower flame temp at the port)
3) there is no evidence to support higher cyclic rate — the opposite is true (faster powder + lower port pressure == lower dwell time pressure, lower force under the curve)
4) there is no evidence to support bolt breakage (same as 3, peak bolt thrust is increased, but peak bolt cam shear forces are decreased)
I’ve been reloading for autoloaders for 33 years and I have broken bolts — and I know why — this article doesn’t seem to add up.
What I do see is evidence that once-fired brass will be useless.
I agree that the claim of the gas port erosion and pressure doesn’t make sense based on the charts shown. However, IF gas port erosion is increased for some reason, it would over time, in theory, increase the cyclic rate as it would allow more gas flow. It would also cause more gas tube failures.
As for bolt breakage, if the port pressure is lower, it should decrease bolts breaking in half, since like you said, the shear is lower. But the huge increase in bolt thrust would cause an increase in stress on the lugs, so it should increase breakage in that area.
Agreed about the reduced usefulness of brass, that much pressure is going to drastically increase stretching and thinning of the walls.
At any rate- it looks like the M855A1 is a huge step backwards in many ways.
Since Bartoucci was the lead tech at Colt, I’d say he knows what he’s stating here.
Would be nice if bolts were forged, instead of cast. And made of higher quality steel. But! Mil-spec is, and always be, the cheapest, lowest quality, that gets by, most of the time. We should be talking 65,000 round capable M-4’s, not 5,000 round!
You have absolutely no idea what you are talking about. Thanks for letting the world know.
Thank you for the excellent article that provides usable information relating to the M855A1 round and the damage that it causes to M4 rifles. Who is John Galt? TEXIT!
Just one data point, strictly for sake of the discussion. The article postulates about bolt breakage. Interestingly this topic came up on ARFCOM and a member who has a full career in Army SF, almost all deployed, and now many years downrange in a support role handling weapons maintenance, fielding new packages, etc., weighed in on that bolt breakage question:
“How many bolts have you replaced? M855A1 became almost standard for range use in Astan after stocks of M855 were depleted. You want to know how many more broken bolts I replaced? Two over 3 years out of hundreds of guns and many types of ammo and round counts. Do bolts occasionally break? Yes, but no more quickly with M855A1 in my experience.”
And he is supporting weapons that are getting fired – a lot. Just thought that interesting.
Ehhhhhhhh…..I’d take that with a major grain of salt.
As in, a salt mine.
Its standard practice to carry a spare BCG due to the issue with 855, exacerbated by 855A1. Its standard practice at the Bravo course, standard practice in line infantry units. Its carried in a ziploc bag coated with lube after checking the headspace. And this is experience at the macro level, not some guy bullshitting creds to keyboard commandos on arfcom. Look up who Chris is.
I’d seriously question anyone saying ‘hey this is fine’ when Colt’s lead tech is saying “yeah, nah.”.
Thanks Chris for taking the time to do true yeoman’s work showing that the Army is lying through their teeth and giving alternative rounds to use.
Thanks Scout for putting this up. You just saved my wife’s AR and the one I’m going to be building soon from PSA, and a relative’s fleet of ARs.
I had to make 20 rounds each of dummy ammo of M855 and M855A1 to use in a class for my unit. I did this by pulling the bullets, dumping the powder, firing the primers, drilling holes in the cases, then reseating the bullets. I used an RCBS kenetic bullet puller (impact type) M855 took 2 hits with maybe a few needing a light 3rd tap to dislodge the bullet. The M855A1 might take 3-5 or it might take 12-15. And I mean smacking the fuck out of the concrete with the tool. The “tar-like” sealant was really holding the bullet in place. I don’t know whether this sealant vaporizes almost instantly upon ignition, but I can’t imagine it not causing inconsistent chamber pressure. Whether it increases chamber pressure in total, I have no idea as that is not my area of expertise. I just found it quite odd. Having handloaded quite a lot of 223 in my day, I have seen the effects of varying neck tension on accuracy and expect this to cause similar variance in velocity/accuracy.