Cmmg Receiver Extension Mk4

The CMMG Receiver Extension Mk4 is a carbine-length buffer tube assembly engineered for AR-15 platform rifles and carbines. Constructed from aircraft-grade aluminum and finished with a hard-coat anodized matte black coating, this receiver extension provides the structural backbone for your recoil management system. The Mk4 profile is a proven design standard across military, law enforcement, and civilian operator builds, offering reliable performance across high-round-count training cycles and duty applications.

Carbine-length receiver extensions are optimized for compact handling without sacrificing buffer mass or spring rate consistency. The hard-coat anodize finish resists corrosion from prolonged storage, salt-air environments, and field use—a critical consideration for operators maintaining weapons in harsh conditions. CMMG's aluminum construction keeps weight minimal while maintaining the rigidity needed for consistent cycling. At 4.5 inches in length, the Mk4 fits standard AR-15 lower receivers and accepts industry-standard mil-spec buffer tubes, springs, and stocks, ensuring full compatibility with aftermarket furniture and upgrades.

This extension suits AR-15 builders prioritizing reliability and modularity—whether assembling a duty rifle, patrol carbine, training platform, or dedicated competition build. Carbine-length tubes are favored for close-quarters work, vehicle mounting, and applications where overall length matters. The CMMG Mk4 serves as a foundational component for shooters who demand precision engineering and proven durability in a straightforward, mil-spec interface.

Carbine-length receiver extensions have become the standard configuration across most modern AR-15 configurations due to their balance of compactness and recoil-spring geometry. CMMG maintains a strong reputation in the tactical community for precision-machined components that adhere strictly to AR-15 specification standards, ensuring fit and function across thousands of rifle builds.