Product Description The Rosco Manufacturing Melonite Bolt Carrier Group is built to MIL-spec standards for modern AR-style carbines chambered in 5.56 NATO / 5.56x45mm and .300 AAC Blackout. Designed with input from both consumers and military end users, this full-auto-rated BCG features a durable Melonite finish for enhanced wear resistance and corrosion protection. It includes a properly staked gas key and a matched, shot-peened bolt that is proof-tested and magnetic-particle inspected to support reliable lockup and consistent accuracy, especially when paired with Rosco barrel extensions. Product Highlights Melonite-coated bolt carrier group for improved wear resistance and corrosion protection MIL-spec construction with a properly staked gas key for dependable cycling Full-auto rated design intended for demanding training, duty, and hard-use conditions Matched bolt is shot-peened and MPI/HPT tested to enhance strength and service life Upgraded extractor and quality component steels support consistent extraction and ejection Specs Brand: Rosco Manufacturing Product Type: Bolt Carrier Group (BCG) Compatibility: 5.56 NATO / 5.56x45mm and .300 AAC Blackout (AR-15 platform) Finish/Coating: Melonite (Black) Carrier Material: 8620 steel Bolt Material: 9310 steel; properly heat treated; shot-peened; MPI/HPT tested Gas Key: 4130 steel; Grade 8 hardware; properly staked Cam Pin: Hardened 4340 Firing Pin: 8740 steel; Mil-Spec; centerless ground; hard chrome coated Extractor: 4340 steel Ejector: S7 tool steel Manufacturer Part Number: ROS-BCG-001 UPC: 181969500821 Disclaimer: We strive to provide accurate and up-to-date product descriptions, specifications, and images; however, errors or omissions may occasionally occur. We are not responsible for any inaccuracies or discrepancies in the content provided. If you notice anything incorrect or unclear, please contact us so we can correct it. When in doubt, we recommend verifying details directly with the product&&';;s manufacturer.