The CMMG Dissent MK4 5.56 16.1" upper receiver group brings CMMG's patent-pending Compact Action direct impingement system to a complete, ready-to-pair upper assembly. Built for shooters who want to go shorter without sacrificing control, the Dissent platform houses the entire action and recoil system in the upper receiver itself—eliminating the bulk and length of traditional AR pistols and giving you a genuinely compact platform that doesn't compromise on ergonomics or shootability. Pair this upper with any mil-spec compatible lower receiver and you've got the foundation for a pistol build, a short-stroke carbine, or whatever your setup demands.

The 16.1" 5.56mm barrel wears a 1:7 twist rate optimized for modern ammunition, backed by a CMMG ZEROED muzzle brake threaded at 1/2 x 28. The real standout feature here is the left-side non-reciprocating charging handle—forward and out of your way when you're running the gun, letting you work the bolt fast without breaking your sight picture. The adjustable gas block gives you real tuning capability: dial it in for suppressed fire, run it hot for your preferred duty round, or find that sweet spot where reliability meets predictability. It's not a set-it-and-forget-it design; it's built for shooters who care about their platform's behavior.

The upper itself is 7075 T6 aluminum with a Cerakote finish, paired with CMMG's 15" proprietary handguard and a 1913 Picatinny rail end cap (included) that replaces the buffer tube position on your lower. The whole assembly runs 5.05 lbs and stretches to 25.5" overall—short enough for vehicle work, confined spaces, or just wanting a rifle that doesn't feel overbuilt. If you're building a dedicated upper collection, stepping up to an AR pistol, or looking for a compact 5.56 that doesn't compromise on gas system sophistication, the Dissent MK4 upper delivers genuine innovation in a straightforward package.

The CMMG Dissent MK4 5.56 16.1" upper receiver group brings CMMG's patent-pending Compact Action direct impingement system to a complete, ready-to-pair upper assembly. Built for shooters who want to go shorter without sacrificing control, the Dissent platform houses the entire action and recoil system in the upper receiver itself—eliminating the bulk and length of traditional AR pistols and giving you a genuinely compact platform that doesn't compromise on ergonomics or shootability. Pair this upper with any mil-spec compatible lower receiver and you've got the foundation for a pistol build, a short-stroke carbine, or whatever your setup demands.

The 16.1" 5.56mm barrel wears a 1:7 twist rate optimized for modern ammunition, backed by a CMMG ZEROED muzzle brake threaded at 1/2 x 28. The real standout feature here is the left-side non-reciprocating charging handle—forward and out of your way when you're running the gun, letting you work the bolt fast without breaking your sight picture. The adjustable gas block gives you real tuning capability: dial it in for suppressed fire, run it hot for your preferred duty round, or find that sweet spot where reliability meets predictability. It's not a set-it-and-forget-it design; it's built for shooters who care about their platform's behavior.

The upper itself is 7075 T6 aluminum with a Cerakote finish, paired with CMMG's 15" proprietary handguard and a 1913 Picatinny rail end cap (included) that replaces the buffer tube position on your lower. The whole assembly runs 5.05 lbs and stretches to 25.5" overall—short enough for vehicle work, confined spaces, or just wanting a rifle that doesn't feel overbuilt. If you're building a dedicated upper collection, stepping up to an AR pistol, or looking for a compact 5.56 that doesn't compromise on gas system sophistication, the Dissent MK4 upper delivers genuine innovation in a straightforward package.