CMMG 57D88C3 Barrel/BCG Kit 5.7x28mm 8" Black

The CMMG 57D88C3 Barrel/BCG Kit is a drop-in barrel and bolt carrier group combination designed to build an AR pistol or SBR in 5.7x28mm. Built around CMMG's patented Radial Delayed Blowback operating system, this kit delivers reliable cycling, reduced recoil, and the flat-shooting performance the 5.7x28mm cartridge is known for.

The barrel is machined from 4140 Chrome Moly steel and finished in Black Salt Bath Nitride for long-term wear and corrosion resistance. At 8" in length, it is optimized for compact AR pistol and SBR configurations. The matched bolt carrier group is engineered specifically for CMMG's Radial Delayed Blowback system and installs directly into a Mk4 or mil-spec AR-15 upper receiver. The kit is intended for use with a CMMG Mk57 lower or other compatible 5.7x28mm-pattern lower receiver.

This listing includes the barrel and BCG only; the upper receiver, lower receiver, magazine, and other build components are sold separately. Whether you are completing a 5.7x28mm AR pistol or assembling a new SBR, the CMMG 57D88C3 kit provides the heart of a proven CMMG Radial Delayed Blowback build.