I have a Rock River 16" carbine. Only thing I have done is add an EOTech, and change the A2 flash hider to a Phantom. I'm currently building an AR. The lower is complete. Stag lower, Cav Arms 6 position collapsible stock and an ergo grip in coyote brown, RRA two stage trigger. The upper is rock river. I'm having a barrel made from a Douglas blank in 6X45mm. It's still in the works, so I'm collecting the rest of the parts while I wait. YHM lightweight 4 rail free float forearm, Leupold MK4 3X9 scope, GG&G extended scope mount, YHM bipod adapter. Haven't bought the bolt/carrier group or gas block yet. Hoping to have the barrel and everything else here by mid April to complete the build.