So, got a 5.56 RRA and currently building a 6.8 SPC in SBA (Super Bad A$$), lol. Accumulating parts for another build (on an AST lower #014). Just bought another Battlecomp compensator BABC, for larger calibers, but don't need to build that next. What do you guys recommend for #3? Can you do .308 of a mil spec AR15 lower or do you need AR10? Other thoughts are 6.5, .300, and .264. Mostly paper punching, but not opposed to getting into hunting/ varmit down the road. Of course, another 5.56 is always an option... So many choices...