Testing The Army’s M855A1 Standard Ball Cartridge

[The Annoyed Man]

American Rifleman has an interesting and informative article about the Army's newer "green" Bronze-tip M855A1 cartridge compared to the older green-tip M855 cartridge, the reasons why the Army and Marine Corps are not standardized on the same cartridge, and how the two cartridges perform in different variations of the M4/M16 platforms......

http://www.americanrifleman.org/article ... cartridge/

[The Annoyed Man]

I like the sounds of this - seems like a decent penetrator on hard cover with much more damage to soft tissue, too.

I find it interesting too, but not entirely convinced. The trouble is that for me and you, this stuff is pretty much unobtanium.

I was particularly interested in the ballistic information about the performance of 1:7 barrels to 1:8 and 1:9 barrels. I already knew that the origins of the 1:7 barrel are found in the need to stabilize the longer tracer bullets, and I know that, generally speaking, tighter twists will stabilize heavier bullets better, but I had forgotten that the original twist rate for the platform was 1:12, and that 1:9 is already a faster twist. It was interesting to me that the 1:9 and 1:8 barrels were almost twice the accuracy of 1:7 barrels with both 55 and 62 grain ball ammunition (regardless of penetrator). My son has a Rock River 24" bull-barreled rifle with a 1:8 twist, and I've watched him put 5 rounds into 1/4" at 100 yards with it, using Black Hills 77 grain OTM.

My wife's carbine is a 1:9. My DMR is a 1:8, and I have settled on a 1:8 polygonal-rifled barrel for the SBR I'm building. But for a while there, I dithered over getting a 1:7 or a 1:8 barrel for it. I settled on the 1:8 before I read this article, but I did it because of A) my accuracy experience with the longer 18" 1:8 match grade barrel on my DMR, and B) my experience with polygonal rifling on several other weapons I either own or have owned in the past.......polygonal-rifled barrels being much easier to clean. It gratifies me to learn that I avoided a potential accuracy trap by going with a 1:8 twist, even though this 10" barrel is going on a primarily CQB oriented weapon.

Interestingly, I had heard all of this stuff before from a customer service rep at Brownells who used to work at Lake City, test firing ammunition batches for QC purposes. He said that he often fired thousands of rounds a day. He told me that the old M855 is still called the SS109 in other NATO countries, most of which remained standardized on 1:9 twist barrels looooong after the US started switching to 1:7 barrels. Most of those nations are still using SS109, and they still continue to experience better accuracy from their barrels.

The thing I find troubling about the M855A1 is not just the significantly increased throat/barrel wear (although, at "only" 6,000 rounds fired, that is troubling), but also the cracking of bolt lugs and cam-pin holes and bolt carriers from the 13% increase in chamber pressure. That is not an insignificant increase in pressure. What the article does not say is if this cracking occurs earlier or later in the testing. Even if we consider barrel life as a consumable, the cracking is just darn dangerous. If a soldier loses incremental accuracy due to barrel wear over the course of several drawn out battles, it does not render him combat ineffective. But a kaboom in his face with the attendant injuries just might do to him what the enemy could not.

So while there is some increased lethality and barrier penetration from the M855A1, it sounds to me like it also represents the upper limits of what can be done with the cartridge. If it is prematurely wearing out barrels and cracking bolts now, how much further can development be taken before the logical conclusion becomes "we need a bigger bullet"?

The author himself, apparently a fan of M855A1, concludes that comparing the effect of 7.62 M80 ball (without a penetrator) to the effect of M855A1 on a 3/8" steel plate at 300-400 yards is not really a valid comparison. Apples to Oranges. What would be a valid comparison would be to compare an "M80A1", with the same kind of penetrator design, against the M855A1.....at 500 yards......against 1/2" plate steel.

It's worth noting that the USMC is still not on board with this cartridge. One could conclude that this is simply a case of inter-service rivalry. On the other hand, with the USMC's long tradition as a highly aggressive, highly mobile light infantry, perhaps they have different institutional requirements than the Army does. The USMC has developed its own "penetrator" bullet.....perhaps not as effective against armor plate, but more effective against flesh and bone......which for the individual marine rifleman may be a higher priority target than steel armor plate.

Lastly, the author points out that the Army has spent large amounts of money on optics with bullet-drop compensating reticles. While he doesn't name them by brand, I assume that he is referring to the ACOG - which both services use in large numbers as part of a basic rifle kit. He also points out that, at distances of 300 and 400 yards, the new ammo prints groups of 6" and 4.5" above POA respectively - thus invalidating the reticle's hold-over hash marks. I own one of those optics. Granted, the military probably gets a better price on them than I can, but they are still quite expensive, and the military-at-large probably owns hundreds of thousands of them. The USMC alone ordered 115,000 of them in their first order, to put one on top of every rifle issued to every marine. God knows how many the Army ordered. I'll bet even the Army doesn't know for sure..... But the Marine Corps spent $7.5 million for the first 6,000 ACOGs, and had a standing order in 2005 of $660 million for more of them (SOURCE). The point is, there are bigger issues than just ammo cost/performance.

Being objective as I can be:

• On the plus side:
  
  • M855A1 is more lethal than M855.
  • M855A1 is more barrier-blind than M855.
  • M855A1 is more environmentally friendly than M855.
  • M855A1 is no less accurate than M855.
  On the negative side:
  
  • M855A1 is more expensive to manufacture than M855.
  • M855A1's 13% higher chamber pressures wears out barrel throats and rifling significantly faster than M855, increasing the per-unit cost of maintaining an individual rifle in service.
  • M855A1 cracks bolt lugs, cam-pin holes, and bolt carriers, while M855 does not, increasing the cost of maintaining an individual rifle in service, and adding some risk to the user.
  • M855A1 is not regulated to the reticle of the most commonly used magnified optic in either infantry service, rendering hundreds of millions of dollars in optics useless beyond close combat.

Nothing happens without a tradeoff, and it seems to me that the 5.56 NATO cartridge - which is a fine cartridge for many purposes, including combat purposes - is now subject to the laws of diminishing returns. The cost tradeoffs necessary to obtain a fairly small incremental performance increase may not be a wise use of development or rearming funds.

I am no kind of expert on military applications, but maybe it is time to go to a heavier standard caliber, or something......or perhaps consider redistributing the type of weapons loadout at the squad/platoon/company levels. I don't know. What I do know, at least from reading this article, is that there are significant tradeoffs involved here that I am not convinced are worth it. Not all of our wars are going to be fought against skinny men with 7" chests.....and it bears pointing out that skinny, 7"-chested men don't often tote steel armor plates around.