These days, I normally just grab one of AIM's. I've got BCG's from quite a few companies and they have all worked fine so far.
BCM makes a great product, but it's just a mil-spec BCG. If I'm going to spend how much they want I'll get an ARP Superbolt (which is my go to for all my 6.8 guns).
Currently I've got bolts/BCG's from AIM, PSA, PTAC, Daniel Defense, Colt, FN, MGI, Larue, Rguns, ARP, Spikes and maybe a few others I've forgotten.