The Rosco Melonite Bolt Carrier Groups are designed to meet the needs of modern carbine shooters. They incorporate input from both consumers and military end users to ensure you get the product you require, not just what they want to sell. All Rosco BCGs conform to MIL specifications and feature a properly staked gas key along with a Melonite coating for enhanced durability. They also include a shot-peened/MP-tested matched bolt (with an upgraded extractor) engineered to lock up precisely with their extensions for exceptional accuracy. These BCGs are built to withstand full-auto rated fire and demanding use from the end user.