300 blackout bolt carrier group

[Swamp]

I am currently piecing together a 300 blackout and I was wondering which type of BCG, full or semi auto, works best with the round. Also the pros and cons of both.

[MarkCO]

Depends on if you are planning on being over-gassed or under-gassed. It is just a weight difference. I tell people to go with the commercial and then use the buffer weights to tune.

[ray1970]

The 300 is typically under gassed unless you plan on suppressing it. As already mentioned, I'd go with the cut bolt carrier. If you decide you need more weight, you can play with different buffers.

[Skully]

Both my AAC 300 BLK 16" uppers came with a M16/full auto BCG and it was recommended by AAC to use a standard Carbine buffer for the 16" barrel and H buffer for the 12.5 and 9" barreled versions.

This works with all Supersonic ammo and Subsonic depending on what you are shooting, some subsonic loads dont cycle right unless it is suppressed.

I dont think using a Semi auto or full auto BCG is going to be a big deal.

[Skully]

From what I have read, specially on the 300BLK Talk forum, you will never overgas a 300 Blk rifle, why NOVESKE went to pistol gas ports on all of their sized 300 BLK barrels, it turned out it didn't matter.


Now I have heard of improper cycle due to to small or too large of a gas port, too heavy of a buffer, etc.

[KS63]

Use whatever BCG that's in your price range. What I think is important for proper function is are you shooting subs or supers, the gas length and gas port size. Like others have said, you can fine tune with buffer weights to get consistent lock back. My barrel has a .108" gas port, carbine length on a 16" barrel. My buffer and spring system is a VLTOR A5 rifle length. This buffer system is heavier than "normal" but has always locked back on empty in part to the .108" gas port.

[Hoser]

I run a standard weight buffer with M-16 carrier. I have my 9 inch set up to run full auto though.