Faxon Firearms 6.8/224 Valkyrie Bolt Carrier Group- Nitride. Improvements include using 9310 tool steel for the bolt nitriding the assembly to increase surface hardness decrease resistance and have superior corrosion resistance compared to typical chrome and phosphasted Bolt Carrier Group BCG. 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 Group BCG are Superfinished to reduce friction increase smoothness of operation and reduce fouling. Further they are full-Auto rated and maintain the trip for full-auto fire control groups and new multi-stage trigger systems. Gas keys use grade 8 fasteners and are fully staked for a lifetime of service. Detailed Specifications: 9310 Tool Steel Bolt Full MIL-SPEC Heat Treatment Shot Peened to MIL-SPEC Magnetic Particle Inspection (MPI) Back of Lugs Chamfered for Reliability Spring Insert Crane O-Ring Installed Salt Bath Nitrided Bolt Carrier S7 Extractor Superfinished Carrier Body Full Auto Compatible Forward Assist Serrations Specifications for Faxon Firearms 6.8/224 Valkyrie Bolt Carrier Group: Manufacturer: Faxon Firearms Color: Black Finish: Black Nitride Fabric/Material: 9310 Steel Caliber: .224 Valkyrie Gun Model: M16 Hand: Ambidextrous Gun Type: Rifle Features of Faxon Firearms Valkyrie Bolt Carrier Nitrided 9310 Tool Steel Bolt Full MIL-SPEC Heat Treatment Shot Peened to MIL-SPEC Magnetic Particle Inspection (MPI) Back of Lugs Chamfered for Reliability Spring Insert & "Crane" O-Ring Installed Salt Bath Nitrided Bolt & Carrier S7 Extractor Superfinished Carrier Body Full Auto Compatible Forward Assist Serrations Package Contents: Faxon Firearms Valkyrie Bolt Carrier Nitrided What firearm models does the manufacturer say Faxon Firearms 6.8/224 Valkyrie Bolt Carrier Group is compatible with? The manufacturer suggests that Faxon Firearms 6.8/224 Valkyrie Bolt Carrier Group is compatible with M16Faxon Firearms FF224BCGCNITRIDE: 6.8/224 Valkyrie Bolt Carrier Group- Nitride