Will a Bushmaster upper receiver match up with my Colt lower?
Our upper will match with old or new Colt lowers, however, Colt made many interim models with a large (larger than mil. spec.) pivot pin. If your front receiver pin is larger than the rear takedown pin, you have one of these Colt models. This causes no problems as we sell an adapter pin that will fit your lower to any of our uppers - or vise versa.