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 phosphated 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. Extractors are S7 Tool Steel. From there, the extractor is sprung using the spring, o-ring, and silicone insert.  *When ordered with a barrel, Faxon personally checks and guarantees safe headspacing. If ordered through the barrel webpage itself, Faxon offers a full matching service with unique laser engraving on both barrel and bolt.  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 QPQ - Salt Bath Nitrided .136" Co-Bore (Type II) Bolt Face for 6.5 Grendel Extractor: S7 Tool Steel Construction Fully Heat Treated Shot Peened Per MIL-SPEC Black Oxide to Match Bolt ***Note*** Bolts 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.