Brownells is the point company for BA 6mm ARC barrels. Talking with their tech people the 6mm ARC will use a 6.5 Grendel Type 2 bolt which will go into a standard sized 5.56 BCG.While I have had what I would call premature failure of an extractor on a Kak 7.62x39 bolt I have yet to break any lugs. This KaK bolt has close to 5000 rds on it now and I also have another 7.62x39 build with a Young manufacturing bolt assembly with well North of 5000 rds with zero failures. Of course my use doesn’t equate to torture testing but for the hunters, competition shooters, or casual plinkers, I would think a bolt could be made plenty robust for the 6mm arc. Woa makes some good barrels but maybe they need to contract with a company like Young manufacturing to make their bolts.