CMMG Dissent Mk4 6mm ARC 16.1in Upper Group 1-7.5 Twist 5/8 X 24 TPI .750in 25.5in Coyote Tan. Combing the flat shooting characteristics of 6mm ARC with the revolutionary DISSENT Compact Action this upper group gives you the ability to build with a new AR15 lower or upgrade your existing DISSENT lower to an instrument with long-range proficiency. Utilizing our patent pending direct impingement Compact Action DISSENT upper groups house the entire action and recoil assembly in the upper receiver resulting in less bulk and length than traditional AR pistols. The forward non-reciprocating side charger allows for quick bolt operation without coming off target. Direct impingement DISSENTS come equipped with a left side charger standard. Right side charging handles for DI models are available here. All DISSENT Upper groups include a 1913 Picatinny rail end plate to use in place of the lower receiver buffer tube. Specifications for CMMG Dissent Mk4 6mm ARC 16.1in Upper Group: Manufacturer: CMMG Caliber: 6mm ARC Overall Length: 25.5 in Barrel Length: 16.1 in Barrel Twist Rate: 1-7.5 Threads per Inch: 5/8x24 Muzzle Device: CMMG Zeroed Muzzle Brake Fabric/Material: Aluminum Gas Block Journal Size-Diameter: .750 in Gun Rail: M-LOK Weight: 5 lb Magazine Included: No Package Contents: CMMG Dissent Mk4 6mm ARC 16.1in Upper Group CMMG 60B2D0C-CT: Dissent Mk4 6mm ARC 16.1in Upper Group 1-7.5 Twist 5/8 X 24 TPI .750in 25.5in Coyote Tan