Cmmg bho

[hapidogbreath]

I put out some heavy coin for a CMMG upper with the BHOA option and 2 mags. Mags needed to be worked in to even feed and I still can't get the bolt to stay open on the last round. Does anyone out there have any idea how long this takes to break in or did I get a lemon. Have tried it on a DPMS lower and a RUGER.

Any help would be great!