CMMG Lower Sub-assy Mk9 9mm Carbine

The CMMG Lower Sub-Assembly Mk9 in Black (91CA2A6-AB) is the stripped lower receiver foundation for CMMG's evolved 9mm platform, engineered to accept Colt SMG-style magazines and built around the company's patented Radial Delayed Blowback operating system. This component serves as the serialized firearm base for builders assembling complete Mk9 carbines or pistols, delivering the mechanical advantage of reduced felt recoil compared to conventional blowback operation.

Constructed to CMMG's specification, the Mk9 lower assembly integrates the trigger group cavity and magazine well geometry optimized for SMG-magazine reliability. The Radial Delayed Blowback system distinguishes this platform by distributing bolt carrier forces radially, minimizing impulse transmitted to the shooter and improving shot-to-shot control. Weighing 1.06 lbs, the compact lower (4.5 × 2.25 × 10.75 inches) facilitates both short-barrel pistol and rifle-length configurations depending on upper receiver selection and local jurisdiction requirements.

This lower receiver is intended for experienced builders and gunsmiths who understand CMMG's Mk9 architecture and assembly procedures. It appeals to operators seeking a 9mm platform with manageable recoil characteristics for training, secondary duty roles, or specialized applications where magazine interchangeability with established Colt SMG inventory is operationally advantageous. The modular design allows customization through choice of upper assembly, handguard, and furniture while maintaining the efficiency gains of the Radial Delayed Blowback system across the platform.