I have a BM Carbon 9MM Ar it is ok, I got on a trade but would of Never spent the $$$$ on one. The upper ond lower don't fit all that well. In 9mm it runs good but a buddy has the 223/5.56 one and he cannot keep the thing running. It has been back to BM twice that I know of and they cant seam to get to run right. (Short strokes all the time with ALL ammo not just low power loads but ALL ammo).
So if I were you I would get some thing other than the BM.

Dave