RRA upper with RRA B/BCG. Has a Wilson barrel with 1/8 twist. I don't know what the significance of the Wilson barrel means. Help with that? Is 1/8 twist ok? What size ammo does that twist like best? It's got 320 rounds through it with a 12" Troy MRF rail, Troy BUIS, Troy low-profile gas block, and 3 Magpuls covers for $725. Good deal?