"We just can't help not accepting the status quo. Bolt carrier groups are available aplenty, but few could meet our exacting standards for performance and value. Seeing ""MIL-SPEC"" as just the starting point, we set out to ensure the best options are available for our demanding customers.  Improvements include using 9310 tool steel for the bolt, which is stronger and nitriding the assembly to increase surface hardness, decrease resistance, and have superior corrosion resistance compared to typical chrome and phosphasted bolt carrier groups. 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.  Technical Specifications Bolt: 9310 Tool Steel Construction (Stronger than C158) 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 Extractor: S7 Tool Steel Construction Fully Heat Treated Shot Peened Per MIL-SPEC QPQ - Salt Bath Nitrided Carrier & Key: Superfinished Carrier Carrier: MIL-SPEC 8620 Steel Material Key: 4140 Steel Material Fully Heat Treated Forward Assist Serrations M16 (FULL-AUTO) Compatible Grade 8 Fasteners Fully & Properly Staked Key, Permatex Sealed TiN PVD & Salt Bath Nitrided Cam Pin:  4140 Pre-Hardended Steel Material QPQ - Salt Bath Nitride Note - Bolt carriers ordered and deployed with barrels not specifically checked by Faxon for headspacing MUST be checked to ensure safe and reliable function. Faxon recommends Pacific Tool & Gauge headspace kits for all measurements. For detailed instructions on headspacing, see our blog post for instructions. "