The AR-STONER(TM) 450 Bushmaster, 458 SOCOM Bolt Carrier Group is a great option for your next AR-Stoner build. Chambered in the highly effective 450 Bushmaster and 458 SOCOM, this BCG is machined to strict military standards. State of the art magnetic particle testing ensures the assembly is free of imperfections and will function flawlessly. Featuring a staked gas key, the AR-STONER(TM) 450 Bushmaster and 458 SOCOM Bolt Carrier Group is drop-in ready.Note: Upon installation, headspace should be verified by a qualified gunsmith. Features Machined to Mil-Spec Standards Properly Staked Gas Key Drop-In Ready Black Nitrite Finish Carrier