M855A1 EPR Gel Tests.

[InfiniteGrim]

Taken down....apparently this is somewhat classified!

[vicious_cb]

Impressive performance, looks to be on par or better than the heavy OTM loads. Got any measurements like neck length? TC diameter?

[InfiniteGrim]

I'm going to be honest with you, I never actually looked into all the measurements and stuff. So I'm assuming "Neck length" is the distance the bullet traveled in the gel before the temporary cavity? Where exactly does the temporary cavity start, because honestly it looks like it started immediately, it just didn't show up well in the pictures.

And you want me to measure the length,height, width of the temporary cavity correct?

[WS6]

Given just this, I wonder why Dr. Roberts said it performed so poorly?

[BufordTJustice]

Given just this, I wonder why Dr. Roberts said it performed so poorly?

He was referring to it's barrier performance. Apparently, if you shoot it through any std barrier or laminate auto-glass (per FBI protocols), it is a sub-par performer compared to bonded SP loads like the GDSP, TBBC, Fusion, etc.....and also to the TSX and the Mk318.

He stated that the barrier performance was what had it far behind the others...his statements were specifically about auto glass being its kryptonite.

Not to mention it's only 7,000 psi off of a proof load (63,000 psi chamber pressure). I will NEVER be firing that in any gun that I own.

I'm sure Doc will chime in here soon.

InfiniteGrim, thank you for posting your findings.

[InfiniteGrim]

He was referring to it's barrier performance. Apparently, if you shoot it through any std barrier or laminate auto-glass (per FBI protocols), it is a sub-par performer compared to bonded SP loads like the GDSP, TBBC, Fusion, etc.....and also to the TSX and the Mk318.

He stated that the barrier performance was what had it far behind the others...his statements were specifically about auto glass being its kryptonite.

Not to mention it's only 7,000 psi off of a proof load (63,000 psi chamber pressure). I will NEVER be firing that in any gun that I own.

I'm sure Doc will chime in here soon.

InfiniteGrim, thank you for posting your findings.

I dont have a picture, but the brass casing had a ejector sweep mark on it, which to me as a reloaded shows its definitely around max pressure. Its a sign to me to STOP adding powder or you might have some serious issues.

[BufordTJustice]

I dont have a picture, but the brass casing had a ejector sweep mark on it, which to me as a reloaded shows its definitely around max pressure. Its a sign to me to STOP adding powder or you might have some serious issues.

Knowing that your Armalite already has a NATO chamber and a midlength gas system, I hesitate to think about what the case would look like coming out of a well-worn M4 with a worn buffer spring, worn extractor and ejector springs, a carbine gas system, and only an H buffer.

I would monitor the brass closely. Running at 63,000 psi means that any amount of bullet setback will essentially create a proof load.

Thanks again for the hard work....as there has been essentially zero data on the M855A1 up until this point.

Also, how did the primer look? Was it cratered and starting to flow around the firing pin into the hole?

[InfiniteGrim]

I will get pictures tomorrow of the casing showing the primer and extra swipes, but here are the specs of the rifle used...

Armalite M15A4
16"CMV w/ PWS FSC556
Carbine Gas System
Semi Auto BCG
H2 Buffer
Wolff Extra Power Spring

EDIT: I will also have full size, correctly cropped photos tomorrow. Not sure why photobucket resized, plus the PC I was using didn't have the photo editing function on windows 7 like my other PC does.

I also just cut up the block of gel inch by inch to see what fragments were in each section.

[DocGKR]

InfiniteGrim--Good job! The gel block measurements you want to record are noted here: https://www.m4carbine.net/showthread.php?t=22323. Obviously you will also want to list muzzle velocity, as well as the physical parameters of the recovered projectile (diameter-RD, length-RL, weight-RW).

WS6, my comments on M855A1 are available, for example here: https://www.m4carbine.net/showthread.php?t=101005.

BufordTJustice--Far from having zero data, M855A1 may be the most tested load in recent history; unfortunately most of that data is not publicly available on the internet in easily digested visual format...

[WS6]

I dont have a picture, but the brass casing had a ejector sweep mark on it, which to me as a reloaded shows its definitely around max pressure. Its a sign to me to STOP adding powder or you might have some serious issues.

All of my 5.56 does. Using a Noveske, Colt, Sabre.