M855A1 Accuracy and Velocity

[Ned Christiansen]

-If I may, as Molon finishes his next installment, this may be of interest:

Something I wrote about in Guns & Ammo a few years ago. Could it be true, the old Viet Nam war bromide of," I stitched him square across the chest and he kept coming!" Patrick Sweeney and I tested this many years ago in a class but I took it further for the article. Patrick's point was that then and now, enemy combatants are likely to be wearing AK chest rigs and indeed, those sturdy AK mags filled with steel-case, steel-jacketed, steel-core ammo pose a viable barrier to the old M193 ammo. Even .45 hardball did not get through in some test shots. The good news is that the new M855A1. Mk 318, and Brown Tips all pretty much say, "Magazines? Were there magazines in the way? I didn't notice."

The fun part was that pretty much every rifle round shot into the chest rig also caused a flare-up of powder from the disrupted ammo.

[markm]

Man. I'd have a hard time shooting into good "clips" and ammo. Even if it was Russian stuff.

[Ned Christiansen]

Brand new Croatian mags donated by AIM Surplus.

[hotrodder636]

-If I may, as Molon finishes his next installment, this may be of interest:

Something I wrote about in Guns & Ammo a few years ago. Could it be true, the old Viet Nam war bromide of," I stitched him square across the chest and he kept coming!" Patrick Sweeney and I tested this many years ago in a class but I took it further for the article. Patrick's point was that then and now, enemy combatants are likely to be wearing AK chest rigs and indeed, those sturdy AK mags filled with steel-case, steel-jacketed, steel-core ammo pose a viable barrier to the old M193 ammo. Even .45 hardball did not get through in some test shots. The good news is that the new M855A1. Mk 318, and Brown Tips all pretty much say, "Magazines? Were there magazines in the way? I didn't notice."

The fun part was that pretty much every rifle round shot into the chest rig also caused a flare-up of powder from the disrupted ammo.

Good to hear that about the MK318, as I have that but sadly no M855A1. I would like to snag some MK318 Mod 1 though!

[Molon]

-If I may, as Molon finishes his next installment, this may be of interest:

Something I wrote about in Guns & Ammo a few years ago. Could it be true, the old Viet Nam war bromide of," I stitched him square across the chest and he kept coming!" Patrick Sweeney and I tested this many years ago in a class but I took it further for the article. Patrick's point was that then and now, enemy combatants are likely to be wearing AK chest rigs and indeed, those sturdy AK mags filled with steel-case, steel-jacketed, steel-core ammo pose a viable barrier to the old M193 ammo. Even .45 hardball did not get through in some test shots. The good news is that the new M855A1. Mk 318, and Brown Tips all pretty much say, "Magazines? Were there magazines in the way? I didn't notice."

The fun part was that pretty much every rifle round shot into the chest rig also caused a flare-up of powder from the disrupted ammo.

Very cool!

[ABNAK]

Good to hear that about the MK318, as I have that but sadly no M855A1. I would like to snag some MK318 Mod 1 though!

I'm glad I snagged some Mk318 several years ago because now you can't find them or the M855A1. All of my AR's that I have zeroed recently have been done with Mk318.

That 7.62x51 A1 load has me intrigued though.....

[markm]

I'm glad I snagged some Mk318 several years ago because now you can't find them or the M855A1. All of my AR's that I have zeroed recently have been done with Mk318.

What is Mk318? The bonded 62 thing? For me/my brain... I don't care about a round that I can't get on a regular basis. M855a1 could be the greatest thing ever, but if you can't get a bunch of it at a good price, WHO CARES?

It makes for interesting academics, and I do like reading about that kind of stuff, but you can't zero, train, and/or practice with it.

[hotrodder636]

What is Mk318? The bonded 62 thing? For me/my brain... I don't care about a round that I can't get on a regular basis. M855a1 could be the greatest thing ever, but if you can't get a bunch of it at a good price, WHO CARES?

It makes for interesting academics, and I do like reading about that kind of stuff, but you can't zero, train, and/or practice with it.

I had bought all of mine back when it was still 'easy' to find. Not sure what changed but yeah, sadly, it is very hard to find now. So I have a little over a thousand of a bullet that I can't replace my stock when I shoot it. I guess best I could do is find the bullet and load my own.

[markm]

I had bought all of mine back when it was still 'easy' to find. Not sure what changed but yeah, sadly, it is very hard to find now. So I have a little over a thousand of a bullet that I can't replace my stock when I shoot it. I guess best I could do is find the bullet and load my own.

That's cool if you can get a stash of it when the getting is good. We got some weird 87 gr BH load that's pretty cool, but we had so little of it (a few hundred rounds), you couldn't build a strategy around it.

[Molon]

Part 2

Hand-Loaded M855A1 Accuracy


When M855A1 was introduced, we were told by people with “inside information” that this new load produced “match-like” accuracy, yet none of these people where ever able to show statistically significant data to support this claim. The test results that I obtained with M855A1 certainly didn’t show “match-like” accuracy.

The Crane Naval Surface Warfare Center has done extensive testing with M855A1 fired from AR-15s mounted in a heavy, sliding machine-rest test fixture. The Crane Naval Surface Warfare Center is involved in developing special munitions and weapons for our warfighters. They’re not interested in sales hype and propaganda; they’re only interested in facts. They’re not driven by profit margin; their goal is providing our Special Operating Forces with the best tools for accomplishing their missions. When it comes to evaluating the accuracy of ammunition Crane uses 10-shot groups.





With newly barreled upper receiver groups mounted in the heavy sliding machine-rest test fixture, M855A1 was only able to produce a 10-shot group average extreme spread of 2.74” at 100 yards with an average mean radius of 0.85”. With a round count of 3,600 rounds through the barrels, M855A1 was only able to produce 10-shot groups with an average extreme spread of 3.84” at 100 yards with an average mean radius of 1.10”.

The Lothar Walther barrel that I used to test the M855A1 for this evaluation had approximately 3,350 rounds through it at the beginning of my M855A1 testing and as we saw it produced an average 10-shot group extreme spread of 2.07” at 100 yards. A 30-shot composite group of the M855A1 from the Lothar Walther barreled AR-15 had a mean radius of 0.63”.

People are often quick to point out that the lack-luster accuracy of legacy M855 manufactured at Lake City is due among other things to the fact that M855 is composed of three different components; the lead core, the steel penetrator and the copper jacket, yet people seem to gloss over the fact that M855A1 is also composed of three different components; the copper core, the exposed steel penetrator and the copper jacket.





We know that the M855A1 that the US Army based their accuracy claims on was not manufactured on the SCAMP machinery at Lake City, but rather the slower BAM machinery. The speed of the SCAMP machinery is significantly faster than the older BAM machinery.

The M855A1 that I evaluated was produced on the SCAMP machinery. These M855A1 projectiles themselves showed quite a bit of variation. As an example, the base to ogive measurements were all over the map.

The picture below shows two M855A1 bullets that I pulled from the lot of ammunition that I tested. The bullet on the left shows a properly shaped base. Notice the beveled heel and the flat base. The bullet on the right has a “ridge” running around the bottom of the bullet and the base is recessed. Apparently, the speed of the SCAMP machinery comes at a cost.





The US mil-spec for the accuracy/precision of the M4 carbine firing legacy M855 from a machine rest allows for an extreme spread of 5.0” for a 10-shot group at 100 yards.




The US mil-spec for the accuracy/precision of the M4 carbine firing M855A1 from a machine rest allows for an extreme spread of 5.6” for a 10-shot group at 100 yards.



It seems rather odd that the M4 carbine needs to have a larger extreme spread to meet the mil-spec when firing the load that supposedly has “match-like” accuracy. Most of my accuracy evaluation data for Colt M4 carbines was lost in a tragic boating accident, but I was able to obtain a 1.24 MOA 10-shot group from a Colt M4 barrel using true match-grade hand-loads (albeit, this group was only fired from 50 yards).



Unlike caliber .30 and caliber 7.62mm ammunition, there has never been a National Match accuracy standard for caliber 5.56mm/.223 Remington ammunition. In 1965, the caliber 7.62mm Match ammunition was standardized as M118. The 1965 lot of 7.62mm M118 National Match ammunition had an acceptance testing mean radius of 1.9” for 10-shot groups fired at 600 yards. At that time, this was the smallest acceptance mean radius ever achieved for National Match ammunition since records were kept, starting in the year 1919. Naturally, the ammunition was tested from machine-rested, bolt-actioned, heavy test barrels.



The composite target pictured below shows the twenty-seven, 10-shot acceptance groups (that’s 270 rounds!) of the 1965, M118 National Match ammunition fired from the test barrels at 600 yards. The small circle has a diameter of 6” and the large circle has a diameter of 12”.




From American Rifleman, September 1965






From American Rifleman, August 1962.



Everything else being equal, a mean radius of 1.9” at 600 yards would have a mathematical equivalent of 0.32” at 100 yards. Now, 100 yards is not 600 yards, but then, a semi-automatic AR-15 is not a machine-rested, bolt-actioned, heavy test barrel either, so I like to use the mean radius of 0.32” for three 10-shot groups fired in a row (30-shot composite group) at 100 yards as the threshold for match-grade ammunition in 5.56mm/223 Remington when fired from a semi-automatic AR-15. A mean radius of 0.32” at 100 yards is equivalent to an average extreme spread of 1.025” for 10-shot groups.

The first step that I took in developing a hand-load using M855A1 bullets was to cull the projectiles with the “ridged” bases.




Next, the bullets were sorted by weight. A group of the bullets within the mean weight were further sorted by their base to ogive measurements and the bullets within this mean measurement were used for the hand-loads.

The cases used for these hand-loads were virgin Lake City cases that were weight sorted. The necks of these cases were then chamfered, deburred and neck sized using a bushing neck die. The primer pockets and flash holes were uniformed. Priming was conducted using a Sinclair hand priming tool.

The cases were charged with powder using an RCBS Match Master powder dispenser and the bullets were seated on a single stage Forster press. 10 rounds of each increment of powder charge weights were used to develop a load at 223 Remington velocities. Most 5.56 loads can be hand-loaded to shoot more accurately/precisely when down-loaded to 223 Remington velocities.




The hand-loads were fired from my bench-rest set-up using the same Lothar Walther barreled precision AR-15 used to test the factory loaded M855A1 and all my usual procedures were followed. The smallest 10-shot group produced in this test had an extreme spread of 1.14” and a mean radius of 0.427” (and a score of 100-10X). Not quite match-grade, but close enough to call it “match-like” I guess.




…..