BC-10 6.5 Creedmoor Forged Upper 20” Black Nitride Heavy Barrel 1: 8 Twist Rifle Length Gas System 15” MLOK Split Rail - $287.65 This BCA AR-10 Complete Upper has a 20" heavy barrel with a black nitride finish, and features a 1: 8 Twist Rate, a Rifle length gas system. It includes the new 15" MLOK