CMMG 55CA9D7 MK4 Receiver Extension Buffer Tube AR Platform Black Steel

The CMMG MK4 Receiver Extension is a steel buffer tube built as a direct replacement for the AR platform. Designed for the MK4 lower receiver family, this receiver extension provides the carbine-length housing that retains your rifle's buffer and recoil spring on the rear of the lower.

Constructed from steel with a black finish, this CMMG buffer tube installs in place of a standard carbine-pattern receiver extension on any compatible AR-15-pattern rifle. The matte black surface matches factory CMMG components for a clean, uniform appearance on a complete build or repair.

Whether you are replacing a worn-out tube or finishing a custom build, the CMMG MK4 Receiver Extension is built to deliver reliable performance as part of your AR-platform rifle.