CMMG Dissent MK4 .300 AAC Blackout

The CMMG Dissent MK4 brings something genuinely different to the 300 AAC Blackout PDW space – a folding stock that doesn’t require a buffer tube thanks to CMMG’s Radial Delayed Blowback system. At $1,799–1,899 street price, this 6.5″ pistol isn’t cheap, but the combination of a true folding aluminum stock, factory SLR adjustable gas block, and a TriggerTech trigger already installed makes a case for itself. This is a subsonic-first suppressor host built for vehicle storage and close-quarters defense, not a hunting rifle.

Quick Verdict

✓ Best for: Compact suppressed .300 BLK PDW and vehicle storage
✓ Price: $1,799–1,899 street
✓ Key strength: Bufferless folding stock at 26″ folded with factory-adjustable gas
✗ Not ideal for: Hunting or anyone wanting full supersonic performance from .300 BLK

Real-World Performance

The 6.5″ barrel with 1:8 twist is built around subsonic .300 BLK, and that’s where the CMMG Dissent MK4 shines – Federal 220gr OTM subsonic loads clock around 1,010 fps for roughly 498 ft-lbs of energy, essentially unchanged from longer barrels since subsonic loads are already tuned for short-barrel velocity windows. Supersonic ammo takes a real hit though; Hornady 110gr V-Max drops to 1,750–1,800 fps compared to 2,100+ fps from a 16″ barrel, which is still functional for close defensive work but noticeably weaker downrange. Accuracy at 50 yards with the subsonic 220gr load runs 1.0–1.5″ groups, helped significantly by the factory TriggerTech AR-D breaking clean at 3.5 lbs. This isn’t a precision rig – it’s a functional PDW platform that handles everything you’d realistically need inside 100 yards, with the understanding that beyond that distance the ballistics start working against you, particularly on the supersonic side where the shortened barrel bleeds velocity the .300 BLK cartridge needs to perform.

Applications & Use Cases

Home defense is where the CMMG Dissent MK4 makes the most sense – folded to 26″, it stores easily in a closet or safe and deploys in seconds, and .300 BLK subsonic through a suppressor offers less overpenetration risk than 5.56 through walls. Verdict: excellent close-range home defense tool. Vehicle storage is the second major use case; at 26″ folded this fits behind a crew-cab seat or in a console box in ways a standard rifle-length AR cannot, making it genuinely practical as a truck gun. Verdict: best-in-class for this role. As a suppressed PDW, pairing the 6.5″ barrel with an 8″ suppressor like the SilencerCo Omega 300 creates roughly 14.5″ of total barrel-plus-can length, and subsonic .300 BLK through that combination is remarkably quiet. Verdict: ideal suppressor host. Hunting is the weak spot – the 6.5″ barrel limits practical supersonic range to inside 75 yards, and most hunters will find a longer-barreled .300 BLK rifle or a different cartridge entirely more appropriate. Verdict: skip this for hunting applications.

Ergonomics & Handling

At 5.8 lbs with the brace attached, the CMMG Dissent MK4 handles light and fast, and the bufferless RDB design means the folding stock doesn’t fight against a buffer tube the way traditional AR folders do. The aluminum stock locks up solid when deployed, with minimal wobble, and folds flush against the receiver for a genuinely compact package rather than just a marketing claim. Loading is standard AR-15 manual of arms – any shooter with carbine experience will be running this within minutes, and PMAG .300 BLK magazines seat and drop free without drama. Balance sits slightly forward of the magwell with a suppressor attached, which is expected given the short barrel, but it’s manageable one-handed if needed. The SLR adjustable gas block is reachable without tools for quick field adjustments between suppressed and unsuppressed use.

Aftermarket & Upgrade Path

Because this is built on standard AR-15 architecture, the CMMG Dissent MK4 accepts the entire universe of AR-pattern accessories – M-LOK attachments, Picatinny-mounted optics, and aftermarket grips all bolt on without issue. The most logical first upgrade is a suppressor; the 1/2×28 threading pairs naturally with something like the SilencerCo Omega 300 ($800), and given the SLR adjustable gas block comes factory-installed, there’s no need to buy an aftermarket gas system to make that suppressor run reliably. An optic is the second practical addition – an Aimpoint Micro T-2 ($900) or a more budget-friendly Trijicon MRO ($550) both suit the fast, close-range role this platform is built for. Unlike a lot of PDW builds where the gas block is the first thing swapped out, CMMG already did that work at the factory, so buyers aren’t stuck spending extra money just to get the gun running smoothly suppressed.

Pros & Cons

Strengths:
✓ Bufferless RDB design enables true folding stock at 26″ OAL folded
✓ SLR adjustable gas block factory-installed – no suppressor tuning purchase needed
✓ TriggerTech AR-D trigger at 3.5 lbs out of the box
✓ Reliable cycling of both subsonic and supersonic .300 BLK loads
✓ Accepts standard 30-round PMAG .300 BLK magazines
✓ 5.8 lbs makes it genuinely easy to carry and store

Limitations:
✗ 6.5″ barrel cuts supersonic velocity to 1,750–1,800 fps, well below 16″ performance
✗ $1,799–1,899 is a significant premium over comparable AR pistol builds
✗ Rifle stock configuration on this barrel length requires an SBR stamp
✗ Subsonic-focused design makes hunting applications marginal at best
✗ Functional accuracy only – not built for precision shooting beyond 100 yards
✗ Standard AR pistol builds achieve similar function for $800–1,000 less

Competitors & Alternatives

The CMMG Banshee MK4 uses the same RDB system at $200 less but lacks the folding stock, which is really the entire reason to pay more for the CMMG Dissent MK4. The CZ BREN 3 300 Blackout runs a piston system and costs $400–900 more, appealing to shooters who prioritize piston reliability over CMMG’s blowback design, while a basic AR pistol build in .300 BLK can replicate core function for roughly half the price if folding stock and factory TriggerTech aren’t priorities.

Who Should Buy This

Ideal for suppressor enthusiasts who want factory-adjustable gas tuning without buying aftermarket parts: the SLR block handles sub and supersonic transitions out of the box. Also ideal for anyone prioritizing vehicle storage, where the 26″ folded length is the deciding factor over any other spec on the sheet. Look elsewhere if you’re hunting with .300 BLK: a 16″ barreled rifle like a standard AR-15 .300 BLK will deliver meaningfully better supersonic performance. Budget-conscious buyers should also consider a standard AR-15 .300 BLK pistol build at $800–1,200, which achieves similar subsonic suppressor performance without the folding stock premium.

Frequently Asked Questions

Also worth a look: the SIG MCX Rattler .300 AAC Blackout for a piston-driven compact option, and the Daniel Defense DDM4 V7 .300 AAC Blackout if you prefer a standard AR layout from a premium maker.

Final Verdict

The CMMG Dissent MK4 earns its premium price through genuine engineering – the bufferless folding stock, factory-tuned gas block, and TriggerTech trigger solve real problems rather than just adding marketing checkboxes. It’s not for hunters or budget buyers, but for anyone building a suppressed .300 BLK PDW for home defense or vehicle storage, this is the most complete factory option available.

The CMMG Dissent MK4 isn’t trying to be everything – it’s a focused, well-executed answer to one question: how do you make a suppressed .300 BLK platform as compact and reliable as possible without compromising on trigger quality or gas tuning. For that specific job, it delivers.