.300 blackout, subsonic Gemtech ammo

[JLas]

I guess about a year ago now, I purchased 1000 rounds of "GEMTECH SUBSONIC 300BLK 187GR"

I run two different .300 blackout AR's, so I think that may be why I didn't notice it until now. When ever I use this Gemtech ammo in one of my rifles, the bolt refuses close all the way and I then have "mortar" the round out of the chamber, rinse and repeat no matter what I try differently...

Now when I drop a Hordnay 300 Blackout 208 GR A-Max in the chamber of the same rifle and let the bolt slam home, it has zero problems closing all the way.

I guess ultimately I am questioning whether this is the fault of the rifle or the ammo.
Looking for any help, advise, or thoughts on this... Thanks in advance

 

[Deaken]

Subbed for info. This is the only ammo I have shot in 300 blk but that's only been ~100 rounds.

 

[Bear44]

Sounds like the chamber on that rifle is tighter than SAAMI spec or the ammo case is over sized. Look up the case dimensions for the 300BK and then put a caliper on the ammo. That should tell you what the problem is.

 

[lostgeorge75]

I seem to recall having to mortar the same ammo out of my blackout a couple of times. The bolt would close fine but it was tight enough I couldn't manually eject it. It shot fine too.