M855A1 SBR gel test

[Andrew Wiggin]

American Reloading had M80A1 and M855A1 projectiles for sale. Gun Broker routinely has M855A1 loaded ammo for sale.

[Andrew Wiggin]

PMAGs can certainly be used in an M249 on an emergency basis, but since it's a belt fed, it prefers...well, a belt! The Aberdeen Proving Grounds document I have indicates the A1 round is loaded to a "higher chamber pressure" than M855, so it's definitely not lower than M855 and if it is then there's no way, Newtonian Laws still holding, that it can have higher velocity than M855 with a lower chamber pressure and the same mass of projectile. I don't care if we wear out M4 bolts and barrels 25% faster (field reports), but I do care if the standard poorly informed shooter loads this in his hobby grade carbine and high orders it. Don't buy this stuff, don't accept this load and don't use this load CONUS. Its juice ain't worth the squeeze.

This part is not necessarily correct. A slower powder can produce higher velocity with lower peak pressure. I'm not saying that's the case here, but it's not a violation of the laws of physics for lower chamber pressure to still produce higher velocity.

[Unobtanium]

PMAGs can certainly be used in an M249 on an emergency basis, but since it's a belt fed, it prefers...well, a belt! The Aberdeen Proving Grounds document I have indicates the A1 round is loaded to a "higher chamber pressure" than M855, so it's definitely not lower than M855 and if it is then there's no way, Newtonian Laws still holding, that it can have higher velocity than M855 with a lower chamber pressure and the same mass of projectile. I don't care if we wear out M4 bolts and barrels 25% faster (field reports), but I do care if the standard poorly informed shooter loads this in his hobby grade carbine and high orders it. Don't buy this stuff, don't accept this load and don't use this load CONUS. Its juice ain't worth the squeeze.

Yes, it can. It depends on pressure curves and average pressure over time, etc. etc. etc. It is loaded 800psi short of M855, currently. There are reloading forums out there with guys using similar charge weights of commercially available SMP-842 and getting identical velocities, safely.

Here ya go:

http://www.tngunowners.com/forums/topic/49004-smp-842/

Primed lake city brass

62 grain SS 109

Crimped

16" AR15

25.7=~3,045

25.8=~3,070

25.9=~3,095

This is in my gun. I assume no responsibility in the data I just posted in your firearm.

Dolomite

His numbers are showing a touch more velocity than the M855A1 factory ammo shows. And he's not complaining about flattened primers or blown primers...He is using a 16" 1/9 twist AR...so you tell me the odds of it being a "spec" gun...Anyway, his final load, if you read the thread, for a 62gr bullet is 25.8gr. Roughly 0.3gr more than M855A1. And he arrived at that number all by himself, it seems, through looking at his brass and the chrony.

In fact, people are RAVING about how accurate and awesome it is. Wear and tear just isn't an issue with the current loading beyond the bores seeing similar reduction in barrel life as other advancements (M855, 70gr TSX, etc.). The parts maintenance schedule has not changed.

Oh, and as an FYI, Liberty's patent information was a bit loose, and a Federal Court overturned the ruling to favor the government. Liberty lost the appeal. I do not know what that means financially for both parties, exactly, or the US tax payer, nor do I feel that this morally exonerates the US government, but it is what it is. This is why you get a GOOD patent attorney...

[Chuck Haggard]

Since when was the P-Mag reauthorized for use by the Army?

[Erick Gelhaus]

Regarding using magazines, regardless of who made them, in a M249 there is the need to double spring them. I ire, this is get/keep that rate at which the magazine feeds consistent with the speed of weapon cycling. While I imagine that would apply to pats I am unable to offer any opinion since I never used a page in a SAW.

[Unobtanium]

Regarding using magazines, regardless of who made them, in a M249 there is the need to double spring them. I ire, this is get/keep that rate at which the magazine feeds consistent with the speed of weapon cycling. While I imagine that would apply to pats I am unable to offer any opinion since I never used a page in a SAW.

Nor am I advocating that. I know nothing about the saw, or how m855a1 interacts with it, but I see no point feeding a beltfed from a mag to use some special bullet.

[Sixgun_Symphony]

Since when was the P-Mag reauthorized for use by the Army?

I can very, very vaguely remember the Army restructing use of the PMAGs now. But I can tell you that no unit (Infantry) I was in ever enforced it whatsoever, and pmag by and large had been very common and popular among rifleman.

Were they before Gen 3 pmags? If so, the feed lip orientation was not as good as pmags Gen 3. The only government tests I am aware of indicate that pmags fix the issue until well beyond useful barrel life.

I cannot vouch for the person who shared the load data for me, but I can vouch for the velocity. They are clocking around 30 to 50fps faster than m855 from the same gun on the same day. I will have to tear down a few rounds to verify the 25.5gr charge weight, and if accurate, will in my mind add even more weight to the statements made to me about pressure, etc. as I have to way to measure that, and simply must take what I am told there.

Back when you indicate you were issued m855a1, it was clocking 3150ish out of a 14.5 and was indeed hot as hell, and I and the Army, apparently, agree with you, and it was softened up at the expense of terminal performance at distance somewhat.

Likely before Gen III

PMAGs can certainly be used in an M249 on an emergency basis, but since it's a belt fed, it prefers...well, a belt! The Aberdeen Proving Grounds document I have indicates the A1 round is loaded to a "higher chamber pressure" than M855, so it's definitely not lower than M855 and if it is then there's no way, Newtonian Laws still holding, that it can have higher velocity than M855 with a lower chamber pressure and the same mass of projectile. I don't care if we wear out M4 bolts and barrels 25% faster (field reports), but I do care if the standard poorly informed shooter loads this in his hobby grade carbine and high orders it. Don't buy this stuff, don't accept this load and don't use this load CONUS. Its juice ain't worth the squeeze.

Wanted to make a note on the M249/M855A1 ... we linked the ammo (and in NO small quantity either! ... Both for testing and possible use in the field) and got the issues I spoke briefly about..Dont recall ever shooting it from a magazine in the SAW.

[Unobtanium]

I can very, very vaguely remember the Army restructing use of the PMAGs now. But I can tell you that no unit (Infantry) I was in ever enforced it whatsoever, and pmag by and large had been very common and popular among rifleman.



Likely before Gen III



Wanted to make a note on the M249/M855A1 ... we linked the ammo (and in NO small quantity either! ... Both for testing and possible use in the field) and got the issues I spoke briefly about..Dont recall ever shooting it from a magazine in the SAW.

I believe around 2009 was when the feed-lip angle for the PMAG was improved to the point that M855A1 should work well from it. However, also note that you may well have been using abusively hot M855A1. I don't know what powder charge the ammo you had was loaded to.

[HCM]

Since when was the P-Mag reauthorized for use by the Army?

AFAIK it was only the USMC which prohibited PMAGS due to the compatibility issues with the M27 IAR /HK 416 magwell and gen 1/2 PMags.

[Unobtanium]

I finally got around to doing some accuracy testing.
Averaging a total of (9) 10 shot groups fired over the span of 2 days, I arrived at 3.59 MOA.
The best group measured 2.07 MOA
The worst group measured 4.707 MOA.

Interestingly, the first groups of the day which were fired with M855A1 (which would be the second total group fired, on Day 1, so NOT the first group total, fired of any day), showed the best precision on both days.

I followed my typical procedure as regards to loading, resting the rifle, and barrel-heat (I let mirage off the suppressor be my quide) as to which I have followed in the past, which has typically produced 1.5-2.0MOA from ammo the rifle likes.