The Faxon 5.56 M16 Bolt Carrier Group, Nitride is a high-performance and reliable upgrade for your AR-15 rifle. This bolt carrier group is designed for optimal performance ensuring durability and longevity. The nitride finish on the carrier and bolt provides added corrosion resistance. The Faxon 5.56 M16 Bolt Carrier Group features a full-auto rated design, making it compatible with M16-style rifles and other firearms that use a similar operating system. All bolts are fully MPI tested to ensure the material is sound and without defects. Bolt lugs are chamfered 45 degrees to ensure reliable action for even the highest pressure hand loads and fast lightweight actions. Faxon Bolt Carrier Groups are full-Auto rated and maintain the trip for full-auto fire control groups and multi-stage trigger systems. Gas keys use grade 8 fasteners and are fully staked for a lifetime of service. Spring, insert and "Crane" O-Ring installed. S7 Extractor.