I'm in the process of putting together a parts list for my 6MM ARC build. I'm going with a Proof Research stainless barrel and JP all the way back. My question is this, is a 6.5 Grendel JP bolt, a JP low mass bolt carrier, a Gen 2 Silent Captured Spring and a TBD adjustable gas block up front the right set up or do I need a standard BCG or something else?