CMMG Dissent Mk4 300 Blackout Pistol – Superb 6.5″ Buffer Tube Free Build

Description

The CMMG Dissent Mk4 300 Blackout is an AR-pattern pistol with no buffer tube. CMMG moved the entire recoil system into the upper receiver, which is why a 6.5-inch 300 BLK builds into a package just 15.7 inches long and 4.8 pounds.

The Compact Action

Every conventional AR needs a buffer tube sticking out the back, because that is where the recoil spring lives. It dictates the minimum length of the firearm and it is why folding stocks on ARs require adapters. CMMG’s patent-pending Compact Action houses the recoil system entirely within the upper receiver. The CMMG Dissent Mk4 300 Blackout therefore ends at the rear of the lower, with a 1913 Picatinny rail cap that takes a brace or stock of your choosing, or nothing at all.

6.5-Inch 300 Blackout Barrel

The barrel is 4140 chrome moly steel with an SBN finish, an MT contour and a 1:7 twist. The 300 Blackout cartridge was designed from the outset to reach full velocity in barrels this short, which is exactly why the two go together so well. Threads are 5/8×24 behind a CMMG ZEROED linear compensator, which pushes muzzle blast forward and away from the shooter rather than out to the sides.

Adjustable Gas Block

The .750-inch gas block is adjustable, and on a 300 BLK that is not a luxury. Supersonic and subsonic loads generate wildly different gas volumes, and running a suppressor changes it again. Being able to tune the gas means the CMMG Dissent Mk4 300 Blackout runs reliably across all of those combinations rather than being set up for just one.

Ambidextrous Side Charging

The DISSENT charging handle is a side charger that can be switched from left to right by the user. Combined with AR-standard ambidextrous controls, that makes the pistol genuinely workable from either shoulder. A side charger also means you can clear a malfunction without breaking your firing grip or reaching over an optic.

ZEROED Fire Control

CMMG fits its ZEROED drop-in single stage trigger, ZEROED pistol grip, ZEROED trigger guard and a 60/90 degree ZEROED safety selector. The short 60-degree throw is faster than a standard 90-degree safety and is selectable to either. Everything is factory-fitted, so there is no upgrade list to work through after purchase.

Size and Suppressor Use

At 15.7 inches overall and 4.8 pounds bare, this is genuinely compact. Add a suppressor to a 300 BLK barrel this short and the result is quiet, controllable and still shorter than most carbines. A Magpul 30-round 300 BLK PMAG ships with the pistol, and the 5.5-inch CMMG handguard leaves room for a light or a hand stop.

Specifications

• Manufacturer: CMMG
• Model: DISSENT Mk4
• Type: Semi-automatic AR-pattern pistol
• Caliber: .300 AAC Blackout
• Capacity: 30, Magpul 300 BLK PMAG included
• Barrel: 6.5 in., 4140 chrome moly, SBN finish, MT contour
• Twist: 1:7 in.
• Muzzle Device: CMMG ZEROED linear compensator, 5/8×24 threads
• Operating System: Compact Action direct impingement, no buffer tube
• Gas Block: Adjustable, .750 in., pistol length port
• Upper Receiver: DISSENT 7075-T6 aluminum
• Lower Receiver: Mk4 forged 7075-T6 aluminum
• Handguard: CMMG 5.5 in. proprietary
• Charging Handle: DISSENT side charger, switchable left or right
• Trigger: CMMG ZEROED drop-in single stage
• Safety: ZEROED 60/90 degree
• Grip: CMMG ZEROED pistol grip
• Rear: 1913 Picatinny rail end cap
• Weight: 4.8 lbs.
• Overall Length: 15.7 in.
• Finish: Armor Black Cerakote
• Manufacturer Part Number: 30A0E33
• UPC: 840442500917

Who Should Buy It

This suits truck and pack carry, home defense in tight spaces, and anyone building a suppressed 300 BLK setup. The absence of a buffer tube means it will take a genuinely folding brace or stock, which almost no other AR can do without adapters.

The CMMG Dissent Mk4 300 Blackout uses a proprietary upper, so standard AR-15 uppers and buffer components do not interchange. It is also expensive, and 300 BLK ammunition costs more than 5.56.

Shooters who want maximum parts commonality should look at a conventional AR pistol, and anyone wanting the cheapest possible practice should compare a 5.56 build in our catalog. Every firearm we list ships to your chosen FFL and is transferred in accordance with federal and state law.

Browse our full firearms catalog for more pistols, rifles and shotguns, and check factory specifications for the CMMG Dissent Mk4 300 Blackout at CMMG before you order. Our team can help with braces, optics, suppressors, ammunition or transfer paperwork.