I got a good deal on a Palmetto State Armory complete carbine lower awhile back and have been thinking about uppers. Decided that I want an M16 carbine style upper with mid-length gas system. PSA finally got them back in so I ordered one. I would have preferred 1:9 twist, but 1:7 is all they had. It should work just fine with 55 and 62 grain slugs, right?