Quoted:
 
I just build a 300 blackout.  I took it to the range today and the rounds would not eject.  I had to pull the charging handle back with both hands to get the casing to eject, it was jammed in there pretty good.  I fired 10 rounds through it and had the same problem with each round.  I was using Remington 125g rounds.  I went home and took the lower off and dropped a round in, then turned the barrel upside down and the round was stuck.  It seems the chamber is not large enough for the round to eject.  Has anyone else had this problem?  Is there a way to fix this or should I just send the barrel back?
 
Thanks
 

Quoted:
I have two of those barrels and both needed a good scrubbing of the chamber to get rid of crap left in there during manufacturing.  Originally, I had the same problem you're seeing until they were cleaned.  If that doesn't work, contact CMMG -- They're good people.