Mil-Spec Bolt Carrier Group Overview This mil-spec Bolt Carrier Group is proudly made in the USA and built for durability and reliability. The Carpenter 158 steel bolt is shot peened, high-pressure tested, and magnetic particle inspected, ensuring it meets rigorous quality standards for dependable performance. The auto-profile carrier is phosphate coated externally and chrome lined internally, providing smooth operation and enhanced corrosion resistance. The chrome-lined, bar-stock gas key is secured with grade 8 fasteners and staked to mil-spec standards, guaranteeing a secure and long-lasting fit. Compatible with 5.56 and 300 AAC Blackout rifles, this BCG delivers reliable performance under hard use, making it an excellent choice for demanding shooters who require consistent function and durability from their firearm components.