[M14E2]

Interesting article on this round in last months American Rifleman. Has anyone tried , or even seen any of this ammo in civilian hands?

 

[russ0861]

I was severely PO'd that being "green" was of higher priority than improved performance of the ammo.

 

[mack7.62]

Improved performance was a design goal, accuracy and terminal performance were improved over M855. Unfortunately this was achieved by increasing velocity, with increased velocity comes increased pressure, M855A1 pressure is running at 62.5K. Before M855A1 62.5K was called a proof round, now it is a combat load. Not only are you unlikely to see any civilian sales it is unlikely that any will be issued CONUS for training use, it is very hard on rifles. Now I would not be surprised if .gov comes out with green training ammo loaded to normal pressures.

 

[TheShooter]

Improved performance was a design goal, accuracy and terminal performance were improved over M855. Unfortunately this was achieved by increasing velocity, with increased velocity comes increased pressure, M855A1 pressure is running at 62.5K. Before M855A1 62.5K was called a proof round, now it is a combat load. Not only are you unlikely to see any civilian sales it is unlikely that any will be issued CONUS for training use, it is very hard on rifles. Now I would not be surprised if .gov comes out with green training ammo loaded to normal pressures.

So the reason us civilians won't see that ammo is because of the pressures?
Or is it because it is hard on rifles?

 

[noob14s]

62k is the ceiling for 5.56 pressures. Stuff like MK262 is up there, your typical varget match load is probably 52k PSI.

 

[leid]

62k is the ceiling for 5.56 pressures. Stuff like MK262 is up there, your typical varget match load is probably 52k PSI.

E2,
I know virtually nothing about the M855A1 cartridge other than it falls under the current political definition of an "Armor Piercing" cartridge. Given its construction, I don't think we civilian shooters will see the M855A1 come available to us any time soon. M855 & M2-AP were specifically exempted from Klinton's 1994 politically defined "Armor Piercing" ammunition restrictions (it was not a ban) in no small part due to the fact that both cartridges had previously been sold thru CMP. I have read that there were some pretty severe problems with M855A1 (high pressure/barrel life/etc) but M855A1 is reported to be in the field right now. For reference: U.S. 5.56MM mil-spec pressure is 58,700 PSI. MAX 5.56MM NATO pressure is generally accepted at 62,350 PSI but the actual conversion works out to be 62,366 PSI IIRC. And the 5.56MM M197 HIGH PRESSSURE TEST cartridge develops 70,000 PSI.

noob,
You are off base thinking that the Black Hills MK 262 MOD 1 cartridge develops "up there" pressure. The BHA MK 262 MOD 0/1 cartridge was designed to meet mil-spec 5.56MM pressure of 58,700 PSI. There is a comfortable pressure cushion designed into the 5.56MM mil-spec. A high temperature stabilized non-canister grade propellant was initially used in the original BHA MK 262MOD 0/1 loadings prior to 2005. In 2005, the propellant was thermally stabilized to an even higher degree. All lots after 2005 LOT 96 used propellant with increased temperature insensitivity. Reason: The M4/M4A1 carbine was sometimes forced to be used in what amounted to a SAW role in the sandbox: leak frog/break contact. This required development of propellants that were thermally stabilized to an even higher degree than called for by mil-spec at that time (-65F to +165 F IIRC). BHA did a lot of fine work getting the MK 262 MOD 1 cartridge where it I today. Most info above comes directly from Jeff Hoffman, co-owner BHA. CRANE NAVSEA published the rest. A very important part of CRANE NAVSEA's testing is seen below. Note the MAX pressure generated in a HOT M4A1 carbine. And that MAX pressure was generated by a cartridge that fully met the then-current 5.56MM pressure mil-spec. Now compare that MAX to the MAX of the LOT 96 with the increased temperature insensitivity: BIG difference! The commercial BHA MK 262 MOD 1 ammunition available to us has the same propellant used in the full mil-spec MK 262 M1 AA53 loading. Only real difference is that commercial lots do not go thru mil-spec inspection protocol. HTH

EDIT: Guys, I am NOT an insider nor do I have any financial interest in BHA. Just another shooter with an AARP card looking for what works best for my needs.

This 2005 data is VERY dated at this point but still useful: BLH prefix lots are MK 262 MOD 1 & LC prefix lot is M855: The BLH 2005 LOT 96 on the right of the graph used the then-new propellant with increased temperature insensitivity.

 

[noob14s]

LOL you tell me I'm off base and then post a chart where the chamber pressures are in the high 50s and low 60s for the 'temp stabilized' powder.

 

[leid]

LOL you tell me I'm off base and then post a chart where the chamber pressures are in the high 50s and low 60s for the 'temp stabilized' powder.

Absolutely. Quite impressive given barrel temperature. CRANE NAVSEA definitely liked what they saw.

EDIT: Something that is not-so-obvious about the AR15/M16/M4 platform: The AR15/M16 was not originally designed nor intended to reach the barrel temperatures now reached with an M4/M4A1 carbine used in what amounts to a SAW role. IIRC, the original limit I read in the '60s on sustained fire was something like 10-12 RPM which was later revised to 12-15 RPM. No sweat! To reach the test temperatures in CRANE's graph required many times that. We are outside original design limits by a very large margin and at least approaching closed-bolt design temperature limits (cook-off). Here's to hoping DOD got it right with the M855A1 cartridge. It will likely see VERY high temperatures in the hands of our men and women in uniform.

 

[Captain C]

My understanding about the potential problems with the cartridge is that the bolts are developing stress fractures at as little as 6k rounds. I wonder if the Sharps "Relia-Bolt" would last longer with this round. I didn't read anything about reduced barrel life that I can remember, but one would assume the "hotter" round would do just that.

 

[leid]

My understanding about the potential problems with the cartridge is that the bolts are developing stress fractures at as little as 6k rounds. I wonder if the Sharps "Relia-Bolt" would last longer with this round. I didn't read anything about reduced barrel life that I can remember, but one would assume the "hotter" round would do just that.

Captain C,
You are going down the same thought process we had when blown bolts started popping up a decade ago. And I am not talking about a bolt or two. One mil-spec M4A1 blew the bolt after less than 1K rounds since NIW. It is my understanding that CRANE documented that carbine. Shooters started looking at different "super bolts"; SOCOM actually went with one of them. I was beginning to think that a bolt manufacturer might have fouled up on the heat treatment of a bolt LOT but bolts were reportedly testing out fine. It all appeared to be overpressure due to propellant instability at extremely high, never-tested temperatures. The propellant was further thermally stabilized and that was the end of any blown bolt problem other than the occasional. Mil-spec bolt life is about the same as the chrome lined barrel so I change them at the same interval. The "super bolts" supposedly had increased life expectancy but that is another story. Bottom line: The "super bolts" were a bandaid that did not address the problem: overpressure caused by abusive rate/volume of fire. And the "super bolts" themselves were problematic; I had (2). We did look at the blown bolts themselves and found they almost always blew in (1) of (2) specific places. The most common, by far, was the bolt lug next to the extractor. Very understandable since that is a relatively weak, unsupported area of the bolt. I had pics but they are long gone now.
The one device I consider to be the Bane of the AR15/M16/M4 is the drum magazine. Blown bolts/deformed gas tubes/melted gas tubes/burned out throats/destroyed barrel accuracy/ruptured barrels are most often found in the company of drum mag users. The AR15/M16/M4 platform is an air cooled weapon platform; you have to let it cool down whenever possible. Big problem with a drum mag is if you have already severely overheated the barrel with sustained fire/violence of action using a drum(s), the propellant in the chambered cartridge is heat soaking at the same time as the weapon is attempting to cool: your Classic Catch-22. And there you are, virtually replicating CRANE's testing above. And CRANE stated that barrel temperatures can reach 400F; their graph above only goes to 330F. Although 2005 data is considered very dated for DOD use, it is still a VERY good read for us almost a decade later: http://dtic.mil/ndia/2006smallarms/marsh.pdf

 

[Captain C]

Thanks for the great information. I am always looking for ways to make my weapons more reliable. I try to study all aspects of the weapon and change parts to more reliable parts when possible. That is why I only purchase certain types/loads of ammunition, upgrade to better BCG's, springs, gas pistons, etc. (depending on which weapon we are talking about)... Which reminds me, I need to get new trigger groups for the Garand and the M-1A as they both have NM trigger groups currently. While extremely nice to shoot, trigger life may suffer due to the mods made to them....

 

[M14E2]

Now I would not be surprised if .gov comes out with green training ammo loaded to normal pressures.

Thought we had that in the frangible round Federal developed? It used a sintered lead-free bullet. Haven't seen it in awhile , but I still have a few boxes.


I thought the 'green' idea behind this round is to eliminate the lead exposure in manufacture , not terminal lead contamination on ranges , though that is a benefit. Many base ranges were shut down to lead contamination of underground water as well as soil.

The Am Rifleman article was informative , but the comparisons to M-193 and M-855 were done in different rifles. Don't recall the particulars offhand , but the Army's test was sorta like comparing apples to oranges to eggs.