I'd suggest the 9mm but just so I can live vicariously through you. In my mind, the 9mm would make an excellent short-medium range carbine. The round can really take advantage of more barrel length than it's usually given.
I really want to build one as my first AR but it will be ages until I can pop that much dough. There's AK business to do first.
What I really, really want is one that takes Glock mags so it will match my daily carry sidearm but the only people who make them are Olympic and I haven't heard great things about them PLUS they don't sell parts, just complete rifles.
