The Brownells M16 6.8 SPC Bolt Carrier Group offers premium performance for AR-15-style rifle chambered in the unique 6.8 SPC cartridge, ensuring reliable and durable service. The Brownells M16 6.8 SPC Bolt Carrier Group features construction using both 8620 and 9310 steel. The bolt face is constructed using the harder 9310 steel, which then undergoes heat treatment and shot peening. The carrier itself is machined from hardened 8620 steel. .224 Valkyrie compatible Quality assured with magnetic particle inspection Rubber insert and spring included in extractor construction Matte-black nitride finish provides reduced friction and increased rust-resistance Mfg: Brownells