Cryptic Coatings 5.56 NATO M16 Bolt Carrier Group - Phosphate

Full mil-spec construction in a manganese phosphate finish — every spec verified before it ships. The Cryptic Coatings 5.56 BCG is a full-profile M16 bolt carrier group machined from 8620 aircraft-quality steel, with a Carpenter No. 158 bolt, HPT and MPI inspection, Grade 8 staked gas key, and tool steel extractor, finished in manganese phosphate for AR-15, M16, and M4 platforms.

The Cryptic Coatings 5.56 Bolt Carrier Group is a full-auto-profile M16 BCG compatible with AR-15, M16, and M4 platforms, machined from mil-spec 8620 aircraft-quality steel with a Carpenter No. 158 bolt, HPT/MPI tested, Grade 8 staked gas key, and manganese phosphate finish.

Four specifications define this BCG's mil-spec quality. The 8620 steel carrier is heat treated to 60–61 RC and chrome lined on the carrier interior and gas key for corrosion resistance and lubricity, providing the hardness and corrosion resistance at the carrier bore surface that sustains reliable cycling across the full service life of the rifle. The Carpenter No. 158 bolt is CNC machined, shot peened per mil-spec, and HPT and MPI tested — high pressure tested to verify structural integrity and magnetic particle inspected to confirm there are no internal defects before the bolt assembly enters service. The Grade 8 gas key fasteners are properly staked per mil-spec, ensuring the key cannot back out under sustained rapid fire where untorqued or improperly staked keys lose gas seal and cause failures to cycle. The tool steel extractor with spring and Viton O-ring provides consistent extraction across the full range of 5.56 and .300 BLK load pressures without the fatigue failure that lesser extractor materials exhibit over high round counts.

Compatible with AR-15, M16, and M4 platforms in 5.56 NATO, .223 Rem, and .300 AAC Blackout. Full-auto profile carrier — backward compatible with all semi-automatic rifles. BCG weight: 11.55 oz.

8620 steel carrier, manganese phosphate finish. Carpenter No. 158 bolt, shot peened. HPT and MPI tested. Shrouded firing pin, chromed.

Built for duty AR-15 builds, high-volume training rifles, and any 5.56 or .300 BLK platform where a fully inspected, properly finished mil-spec BCG is the requirement.

By Cryptic Coatings. HPT and MPI tested. Standard Cryptic Coatings warranty applies.