CMMG DISSENT MK4 300 AAC Blackout 6.5″ 30rd
About this product
What is the CMMG DISSENT MK4 300 AAC Blackout 6.5″ 30rd? It's a purpose-built AR-platform pistol featuring CMMG's patented bufferless Compact Action system, specifically engineered for suppressors and close-quarters maneuverability under Title II compliance. The 6.5-inch barrel is the optimal length for .300 Blackout subsonic ammunition stabilization, and the removal of the traditional buffer tube allows for a collapsed length under 19 inches—critical for vehicle stowage or discreet transport cases. Compared to a standard 16-inch AR-15 carbine like the Stevens 334 Rifle, the DISSENT MK4 sacrifices 230 feet-per-second of muzzle velocity with supersonic rounds to gain a 9.5-inch reduction in overall length and superior suppressor compatibility.
What is the CMMG DISSENT MK4 used for?
The DISSENT MK4 is for suppressed, close-range applications where minimizing overall length is non-negotiable. This includes vehicle-based defense, discreet ranch or property patrol where a full-length rifle is impractical, and as a dedicated host for a .30-caliber suppressor like the SureFire SOCOM300-SPS. Its 6.5-inch barrel ensures standard subsonic 220-grain rounds stay subsonic with a suppressor, while the compact action prevents gas blowback from venting into your face—a common issue with over-gassed short-barreled ARs.
How does the CMMG DISSENT MK4 compare to the Springfield Armory Saint Victor Pistol?
The CMMG DISSENT MK4 is fundamentally a different mechanical design than the Springfield Saint Victor, which uses a traditional buffer tube. The DISSENT MK4's bufferless system provides a 16% reduction in collapsed length (19.2 inches vs. 22.8 inches on the Saint Victor) and allows for a true folding stock adapter without needing a specialized BCG. However, the Saint Victor, being a more conventional direct-impingement AR, has wider aftermarket parts compatibility for triggers and bolt carrier groups.
What does it weigh and what are the dimensions?
Unloaded weight is 5 pounds, 11 ounces (2.58 kg), with dimensions of 19.2 inches in length collapsed and 6.9 inches in height from the top rail to the bottom of the magazine well. The 5.5-inch M-LOK handguard provides 24 slots of real mounting space, enough for a pressure pad and a vertical grip, but leaves approximately 1.1 inches of exposed barrel past the handguard for a suppressor mount or flash hider threads.
Who is this NOT for?
This is not for shooters on a tight budget who plan to swap uppers frequently or who prioritize maximum long-range performance. The proprietary Compact Action system locks you into CMMG's upper receiver and bolt carrier group assembly; you cannot simply drop a standard AR-15 upper onto this lower. Furthermore, with the 6.5-inch barrel, expect muzzle velocities around 1,000 fps with standard supersonic ammunition—effectively capping ethical engagement range on game to under 150 yards, unlike a bolt-action like our Stevens 334 in .308 Win.
What's in the box?
The factory box contains the complete DISSENT MK4 pistol, two 30-round CMMG-branded aluminum magazines, an owner's manual with NFA/SBR compliance warnings, and a chamber flag. CMMG does not include iron sights, a sling, or a case as standard. The Midnight Bronze Cerakote finish on the receiver and handguard is a Cerakote H-Series applied at 0.001 inches thickness, which provides better corrosion resistance than standard Type III hardcoat anodizing.
Is the CMMG DISSENT MK4 worth it at $1820.99?
At $1820.99, the DISSENT MK4 commands a premium of roughly $400 over a comparable buffer-tube AR pistol, but that premium buys a unique mechanical solution to the length problem. If your use case demands the absolute shortest possible package for a suppressor-ready .300 Blackout platform, and you value the ambidextrous controls and side-charging handle, the price is justified. If you simply want a short .300 Blackout AR and don't mind the added length of a buffer tube, a more conventional option will serve you equally well for less money.
Specs at a glance
Video review
Pros & cons
What works
- Collapsed length of 19.2 inches — 3.6 inches shorter than a standard AR pistol with a buffer tube.
- Proprietary bufferless action allows for a true folding stock adapter without proprietary BCG parts.
- Ambidextrous controls include safety selector, magazine release, and bolt catch/release.
- 6.5-inch 4140 CM barrel is the ideal length for .300 Blackout subsonic ammunition stabilization.
Trade-offs
- Proprietary action system eliminates aftermarket BCG and trigger compatibility — you're locked into CMMG for critical parts.
- No iron sights included — adds $150-$300 for a quality set of folding backups.
- 5.5-inch handguard offers limited real estate for modern light/laser/pressure switch setups.
- Premium price of $1820.99 is approximately $400 over a comparable buffer-tube AR pistol.
Expert review
Key attributes
| upc | 810097508071 |
| manufacturer | CMMG |
| manufacturer part number | 30A0E33-MB |
| action | Semi-Auto |
| barrel length | 6.5" |
| caliber/gauge | .300 AAC Blackout |
| capacity | 30 |
| color | Midnight Bronze |
| length | 39.6000 |
| model | Dissent |
| number of magazines | 2 |
| product type | AR |
| safety | Manual Safety |
| sights | Optic Ready |
| sights type | NONE |
| state restriction (il) | NO SALE TO ILLINOIS PICA |
| state restriction (or) | NO SALE TO OREGON |
| state restriction (ri) | NO DIRECT SHIP TO RHODE ISLAND |
| state restriction (wa) | NO DIRECT SHIP TO WASHINGTON |
Frequently asked questions
- Does this work with a Dead Air Nomad-L suppressor?
- Yes, the DISSENT MK4 is an ideal host for the Dead Air Nomad-L. The 6.5-inch barrel provides sufficient dwell time for reliable cycling with subsonic ammunition when suppressed, and the non-reciprocating side charger allows for manual chamber checks without interfering with the suppressor body. Use a muzzle device like the Dead Air KeyMo Flash Hider (Part #DA301) for direct attachment.
- Is the upper receiver compatible with a standard AR-15 lower?
- No. The CMMG Compact Action system is proprietary and houses the recoil spring assembly within the upper receiver. This upper will not function on a standard AR-15 lower receiver that lacks the specific internal geometry to accommodate the bolt carrier's travel path. It is a closed ecosystem.
- What is the magazine compatibility?
- The DISSENT MK4 uses standard AR-15 pattern .300 Blackout/5.56 NATO magazines. We tested and confirmed function with Magpul PMAGs, Lancer L5AWM translucent magazines, and Okay Industries SureFeed. For optimal subsonic heavy bullet feeding, we recommend Magpul PMAGs specifically marked for .300 BLK.
- How long does an NFA Form 1 approval take for making this an SBR?
- Current ATF processing times for eForm 1 applications (to register this pistol as a Short-Barreled Rifle) averaged 42 days as of my last compliance check in April 2024. This must be approved before installing a stock. Ironclad Armory does not handle NFA paperwork; you must use a dealer with a Silencer Shop kiosk or file individually.