Why a BCG from Griffin Armament? The simple answer is that these BCGs are the best we have used in our ten years of military service and over a decade of industry involvement. When you look at a top shelf product you can see its quality. These are the best mil spec pattern there are. The Griffin BCG combines an 8620 carrier, 9310 Bolt, 4340 cam pin and extractor. All the proper heat treats, the correct shot peen, and the often neglected post heat treated grind are present. In a market filled with cast component BCGs, all components are billet machined and all surfaces receive a finish pass in machining for improved surface smoothness. There are varying degrees of quality in Melonite QPQ finishes. These BCGs went to 4 finishing houses for selection of the finish provider, cost not being a consideration. The result is a deep black finish with remarkable lubricity. These are assembled to the current military technical data package with permatexd and properly staked carrier keys. They also feature the current 15,000 round extractor spring design and a Crane O ring for reliable extraction in extreme conditions. We ran these thousands of rounds in multiple manufacturers rifles throughout the T&E phase without a single malfunction. From first sight through months of use to the final product launch we have remained excited to bring this BCG to market. This is the only BCG that has ever excited us and that is why we have chosen to offer it to the people we care about, our customers. Many Metallurgists consider AISI 9310 alloy steel as an acceptable bolt material and substitute for Carpenter 158 (Carpenters brand name AISI P6 Spec mold steel). However for the M4 purists we offer our BCG with the optional Carpenter 158 bolt made to current Mil-Spec including phosphate rather than Melonite treatment which comes with the 9310 bolt. Specifications for Griffin Armament Enhanced Mil Spec Bolt Carrier Group (BCG): Manufacturer: Griffin Armament Color: Black Finish: Melonite QPQ Fabric/Material: 4340 Alloy Steel, 9310 Steel, 8620 Alloy Steel Cartridge: 5.56x45mm NATO, .300 AAC Blackout Gun Make: AR Platform Included Accessories: Cam Pin and Extractor, Crane O-Ring, Gas Key, Carrier, Bolt Condition: New Bolt Material: 9310 Steel Carrier Material: 8620 Steel Features of Griffin Armament Enhanced Mil-Spec Bolt Carrier Group BCG: 8620 Carrier. 9310 Bolt MP inspected, High Pressure Tested (Carpenter 158 available). Bolt properly heat treated, shot peened, and post heat treat ground with headspace held to half the blueprint specification. 4340 Cam Pin & Extractor. Finish Pass Machined on all surfaces. Full Billet Construction. Premium Melonite QPQ Finish. Latest 15k round Extractor Spring Design. Crane O-ring for increased extraction reliabilty in extreme conditions. Billet machined gas key, installed with permatex and staked to current TDP. Package Contents: Griffin Armament Enhanced Mil Spec Bolt Carrier Group