BiMart Federal XM193 ammo

jdub75 · Jan 27, 2011

I've been grabbing a box here and there of BiMart's 5.56 ammo when it goes on sale & finally shot a few mags of it yesterday. 3 out of 3 times, the bolt didn't lock back on empty. This usually happens when I use PMC, but didn't expect this on what I thought is a 'hotter' load.
Wolf, Tula, custom 69 gr reloads, gunshow 55gr reloads will all lock back my bolt on empty, but this stuff didn't.
Its not the mag, either. I do have a heavier buffer (H2) installed. I could go back to the H buffer, but would rather not.
I've heard anecdotally the BiMart stuff is 2nds, could it be these are not loaded to spec? The fireball from my barrel says otherwise tho...(10.5" SBR).
TIA.

jmac3434 · Jan 27, 2011

huh im going to keep checking this out, i just put 600 rds of the federal that i got when it was on sale a few months ago. i personally had no issues what so ever but my buddy that i was shooting with had the same issue but not with the federal rds. i cant remember what he was shooting.

nubus · Jan 27, 2011

Could be your gas system, could be your buffer.
You aren't giving it much time to build Pressure with a 10.5" bbl.
The same load in a 20" might lock the action every time.
Less to to with hot/light load than specific powder and bullet weight in your setup.
If it's seconds it's cosmetic only. They could not sell it if it was not SAAMI spec.

nubus · Jan 27, 2011

Oh yeah, does that SBR have a carbine or pistol length gas system on it?

jdub75 · Jan 27, 2011

Carbine length piston/gas system. Yeah, I might go back to the H buffer. I used it for some time with no issues. Once I changed stocks I put in the H2 the upper mfr included with their upper. Makes sense what you're saying.

PS I just might throw this stuff up on the classifieds...it a friggin fireball out of the 10" barrel! I'm gonna shoot some at night next week & try to have someone photograph it.