Pistol stabilizing braces have drawn regulatory scrutiny for years, leaving AR pistol builders wondering what would come next. DISSENT is CMMG’s answer. The CMMG Dissent MK4 Upper Group in 5.56x45mm NATO (brand part number 55B8D86AB) packs a 10.5-inch barrel, a left-side charging handle, and a Zeroed Blast Compensator into a compact upper receiver assembly. Utilizing CMMG’s patent-pending Compact Action and Radial Delayed Blowback technology with a fixed ejector, the DISSENT upper group houses the entire action and recoil assembly inside the upper receiver, resulting in less bulk and overall length than a traditional AR pistol. The forward, non-reciprocating side charger allows quick bolt operation without coming off target, and the upper ships with a 1913 Picatinny end plate to use in place of a lower receiver buffer tube.

Key Specifications

• Chambered in 5.56x45mm NATO, giving this compact upper its cartridge-specific ballistics.
• Barrel length measures 10.5 inches, a core part of the DISSENT’s compact footprint.
• Rate of twist is 1:7, matched to standard bullet weights for this caliber.
• Operating system is CMMG’s Compact Action with Radial Delayed Blowback technology.
• Uses a fixed ejector, with the entire action and recoil assembly housed inside the upper receiver.
• Charging handle is a left-side, forward, non-reciprocating design for quick manipulation without breaking your sight picture.
• Muzzle device is CMMG’s Zeroed Blast Compensator, tuned for this caliber and barrel length.
• Handguard measures 9.6 inches with M-LOK accessory mounting slots.
• Includes a 1913 Picatinny end plate in place of a lower receiver buffer tube for a compact pistol build.

Frequently Asked Questions

Is this bare upper itself an NFA-regulated item? No. It is an upper receiver assembly with no lower receiver included, so it is not a regulated firearm on its own. Installing it on a shouldered, rifle-configured lower without a registered short-barreled rifle would require ATF Form 1 approval first.

What makes the DISSENT different from a standard AR pistol upper? The DISSENT houses the entire action and recoil assembly inside the upper receiver using CMMG’s Compact Action and Radial Delayed Blowback system, resulting in a shorter, less bulky package than a traditional AR pistol built around a standard buffer tube.

Is this a complete rifle? No, this is an upper receiver assembly only with no lower receiver included. It ships without an FFL transfer and needs a compatible lower to complete a build.

Buy the CMMG Dissent 5.56x45mm NATO Upper Group

Order this CMMG Dissent MK4 upper group in 5.56 from a Lubbock, Texas gun shop for your next compact AR build. Browse more complete uppers in our AR15 uppers selection.