Thanks, and we both know that list could be much much longer, lolOriginally Posted by Doug MacRay
Thanks, and we both know that list could be much much longer, lol
Several people have asked me where I am getting my data from on M855A1. Well, some of it comes from .mil sources. This .pdf mirrors what I've been saying about the chamber pressure of M855A1, at 54,200, while M855 is higher at 55,000. Sadly, the .pdf no-longer works, but here is the Google remnants of it, red added for emphasis:
But that wasn't good enough for me. No, I wanted to find out for myself, so I went to the local WalMart and picked some M855A1 up myself. Prior to this, I researched what handloaders have been doing wtih SMP-842. Here is what I found:St. Marks Powder
www.dtic.mil/ndia/2006smallarms/faintich.pdf
May 16, 2006 - Propellant 5.56mm round. Velocity(ft/s) Pressure(psi). WC 844. Standard M855. 3020. 55,000. SMP® 842 Green 5.56mm. 3020. 54,200 ...
https://www.tngunowners.com/forums/topic/49004-smp-842/
Cool...I am getting 3059fps average out of MY 16" gun (with Surefire Suppressor) with M855A1...
I just read the velocities on their brochure. I am pushing a 62 grain bullet to 3,070 out of a 16" gun using the SMP 842 without signs of pressure.
Dolomite
FYI, the velocities were impressively consistent.
3077
3056
3073
3037
3035
3077
3073
3069
3058
3035
ES: 42fps
SD: 17.5
Unfortunately, the ammunition I had was variable in accuracy. The best group measured approximately 2 MOA, while the worse measured over 4 MOA, with the average of half a dozen 10 shot groups being 3.55 MOA. The rifle itself typically averages 1-1.4MOA with me behind it shooting 75gr Gold Dot .223, and is a 16.1" Daniel Defense CHF .gov profile barrel with a Nightforce 1-4 on top and a Surefire 556-212 on the end. Other people and entities who are testing M855A1 are showing <2 MOA from it. I believe that it is very possible that I got some ammunition that failed accuracy QA/QC, which is why wal-mart ran a sale on it.
To compare, the MK318 SOST was averaging around 2-2.5 MOA for me out of the same rifle, as I recall, but those were verified "Firsts" from an LE distributor who ships direct from Federal.
Okay, now we know the charge weights that equate to what velocities that one loader is getting with M855A1's powder, SMP-842, while using M855 legacy projectiles (of the same weight). He's getting 3045fps from his 16" rifle using SMP-842 25.7gr in LC primed brass. And I'm getting 3059fps from M855A1...so let's crack one open and see how things stack up!
My experience has been this:
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
Okay...people have, on their OWN, with no knowledge shared, worked up AN IDENTICAL load to what the US military is using, and are getting IDENTICAL VELOCITIES using IDENTICAL WEIGHT BULLETS in IDENTICAL CASES with IDENTICAL CHARGES OF THE SAME POWDER and are seeing NO PRESSURE SIGNS. I would also note that IDENTICAL powder charges net IDENTICAL velocity results between M855 legacy, and M855A1, when using the same cases and SMP-842 powder. This seems to indicate, to me at least, that the M855A1 projectile itself is not causing increases in pressure, or we'd see a corresponding increase or decrease or SOMETHING with velocity...
I have previously cited open source government data regarding reliability testing, etc. about M855A1, but actually putting my hands on it, weighing the charges, comparing velocities with handloaders using the same components...it makes the theoretical, tangible.
All this said, chamber pressure CAN have an effect on component life. However, historically, the military has not given a damn. A perfect example is the 1984 USMC test using the M16A1 and M16A2 and M193 and M855 (which had a few thousand PSI higher chamber pressure). In 6,000 rounds, the M855 firing weapons saw drastic accuracy reduction, while the M193 firing rifles saw virtually none. (MK262 also saw issues when CRANE was adopting it...but noone bags on MK262...)
However, this is not what I am hearing about M855A1 and barrel life, but even if it WERE, M855 vs. M193 set the standard regarding how this little saga is going to play out. As did the move from the rifle to carbine gas system. The US military has a long history of sacrificing durability for CAPABILITY, and that's what is going to happen here, especially considering that everything I can put my hands on seems to indicate that only realistically 10-20% durability has theoretically been lost.
Just my .02, and how I arrived there.
Last edited by Unobtanium; 12-29-2016 at 10:38 PM.
No one mentioned ethics - I asked about illegal.
I've lived in 5 states as an adult. One requires expanding ammo for handgun hunting and prohibits lead ammunition for hunting. The other four have no ammunition restrictions other than prohibiting big game hunting with rim fires.
What were these states if you don't mind me asking? I listed the first 10 states I could find with a simple Google search, but I'd be surprised if most states didn't have similar restrictions.
"I need your help. I can't tell you what it is, you can never ask me about it later, and we're gonna hurt some people."
Texas doesnt have a restriction on FMJ, for varmint or game.
Reply With Quote