Semi-Auto/ Full Auto M16 Complete bolt carrier group made by Young Manufacturing Inc. using MILSPEC quality steel on our in-house CNC machines. All carriers are then heat-treated, hard-chromed and each carrier is chrome-lined in the bolt throat. Standard MIL-SPEC carrier with additional care taken during machining process Sharp edges and rough finishes eliminated. Will NOT shred fingers and operates smoothly Hard chromed after heat treatment Made of same steel and using same processes as our National Match but to standard MILSPEC design The HMB Bolt by HM Defense eliminates the pass through cam pin hole and replaces it with a cam pin socket and radiused cam Mfg: Ke Arms