Black River Tactical Full Auto Bolt Carrier Group BCG for the AR Family of Weapons (AR15, M16, M4)
Carpenter 158 bolt is Shot Peened, HP tested and MP inspected.
The USGI full auto bolt carrier is Hard Chrome lined inside and Manganese Phosphate coated outside.
The Mil-Spec gas key is chrome lined, secured with mil drawing heavy splined fasteners and properly staked to ensure reliable gas system performance.
Bolt is marked "MP". Carrier is marked "BRT" with Logo on the ejection port side.
100% made in USA to current USGI M4A1 specifications.