I would like to build a military grade M-4 copy. I am thinking of using the below listed parts and a RRA lower. RRA Lowers fit tightly and I don't like the sloppy upper/lower fit. That is the only reason that I'm using them.

BCM 16in, 1-7 Twist, M-4 Upper
RRA LPK
CMT or LMT BCG
CMT Collapsable Buttstock
H-2 or H-3 Buffer

Any opinions to the contrary, or am I headed in the right direction?