CMMG Dissent MK4 30BC239AB | .300 AAC Blackout 10.50″

The CMMG DISSENT MK4 upper (30BC239AB) is a compact AR-platform upper chambered in .300 AAC Blackout with a 10.50″ barrel and a 9.60″ M-LOK handguard. It uses CMMG’s patent-pending Compact Action and radial delayed blowback architecture with a fixed ejector to house the action and recoil assembly in the upper receiver, reducing overall bulk and length compared with traditional configurations. A forward non-reciprocating left-side charging handle enables quick bolt manipulation while maintaining a sight picture. The upper includes a zeroed linear compensator and a 1913 Picatinny rail end plate for use on AR-platform builds.

Product Specifications

• The model is CMMG Dissent MK4 (30BC239AB).
• The caliber is .300 AAC Blackout.
• The barrel length is 10.50″.
• The barrel finish is Black.
• The overall finish type is Armor Black.
• The handguard type is 9.60″ M-LOK.
• The handguard finish is Armor Black.
• The rate of twist is 1:10″.
• The charging handle is left side, non-reciprocating.
• The muzzle device is a zeroed linear compensator.
• The upper includes a 1913 Picatinny rail end plate.
• This part is listed to fit AR-platform rifles/assemblies.
• The barrel length range is 10″ to 10.99″.
• The category is AR15 Uppers.
• The product UPC is 810097509115.

Compact and purpose-built, the DISSENT MK4 upper is designed for shooters who need a short, controllable AR-platform upper that preserves functionality in a smaller package. Its compact action and left-side charging interface make it well suited to compact AR pistol builds and short-barrel configurations for close-quarters target work and suppressed shooting. The combination of a dedicated compensator, M-LOK mounting, and Picatinny end plate offers a practical baseline for a variety of compact-purpose builds.