I've got a 556 10.5" psa with a flash can and a 12" MI SS rail on one of my sbr's.. Very nice gun, and one of my other sbr's I have a radical arms 10.5" 7.62x39 w/ MI 9.3" keymod, very accurate pig popper
I was on a quest for kind of a specific configuration myself. Im currently building a 10.5" 5.56 upper with a faxon pencil barrel. That paired with a 9.7" SLR rail will make for a nice set up with the Omega 30.