CMMG DISSENT Mk4, 5.56x45mm NATO, 6.5in Upper Receiver Review

First Impressions of CMMG DISSENT Mk4, 5.56x45mm NATO, 6.5in Upper Receiver

The CMMG DISSENT Mk4, 5.56x45mm NATO, 6.5in Upper Receiver is a bold step forward in compact AR-platform technology. CMMG has carved a niche for themselves by thinking outside the buffer tube, and the DISSENT is their answer to the ever-evolving landscape of AR pistols and the legal uncertainties surrounding braces. Its innovative design promises the power of 5.56 in an incredibly small package, and that’s a promise that immediately piqued my interest.

I was looking for a highly concealable yet potent AR-platform upper receiver to pair with a dedicated pistol lower. Existing braced pistols always felt slightly unwieldy. The DISSENT’s bufferless design offered a tantalizing solution to this problem.

Unboxing the CMMG DISSENT Mk4, 5.56x45mm NATO, 6.5in Upper Receiver was a treat. The finish was impeccable and the side-charging handle felt robust. Its compact size was immediately apparent.

Compared to other short-barreled AR uppers, such as those from Bravo Company or Daniel Defense, the DISSENT stood out due to its complete action being contained within the upper. I considered the Maxim Defense PDX, but its proprietary buffer system seemed less flexible than the DISSENT’s 1913 Picatinny rail interface. Ultimately, the CMMG‘s innovative approach and potential for diverse lower receiver configurations sold me.

My initial impression was one of excitement mixed with healthy skepticism. Could CMMG really deliver reliable 5.56 performance in such a small package? I was eager to find out.

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Real-World Testing: Putting CMMG DISSENT Mk4, 5.56x45mm NATO, 6.5in Upper Receiver to the Test

First Use Experience

My first range trip with the CMMG DISSENT Mk4, 5.56x45mm NATO, 6.5in Upper Receiver was at an outdoor range on a sunny, albeit slightly breezy, day. I paired it with a Sig Sauer MPX lower receiver with a folding brace. The ammo was a mix of 55-grain and 62-grain FMJ.

The DISSENT cycled flawlessly with both types of ammunition. The side-charging handle was intuitive to use, and keeping my sight picture during reloads proved to be a definite advantage. I did notice slightly increased muzzle flash compared to my 10.5-inch AR pistol, which was to be expected with the shorter barrel.

The ergonomics took a little getting used to, primarily due to the lack of a traditional buffer tube. It felt more like shooting a large pistol than a short rifle. There were no immediate issues, and the initial experience was encouraging.

Extended Use & Reliability

After several months of regular use, the CMMG DISSENT Mk4, 5.56x45mm NATO, 6.5in Upper Receiver continues to impress. I’ve put approximately 1000 rounds through it. It has shown no signs of significant wear and tear.

The **Cerakote finish *is holding up remarkably well*, even after being bumped around in my range bag. Routine cleaning is straightforward. The direct impingement system requires standard AR cleaning procedures.

Compared to my previous AR pistol builds, the DISSENT is significantly more compact and easier to transport. It outperforms them in terms of concealability while maintaining comparable accuracy at typical pistol ranges (5-50 yards). I appreciate the reliability and innovative design.

Breaking Down the Features of CMMG DISSENT Mk4, 5.56x45mm NATO, 6.5in Upper Receiver

Specifications

The CMMG DISSENT Mk4, 5.56x45mm NATO, 6.5in Upper Receiver boasts some impressive specifications:

• Caliber: 5.56x45mm NATO. This provides ample stopping power in a compact platform.
• Barrel Length: 6.5 inches. This is incredibly short, maximizing concealability.
• Barrel Twist Rate: 1-7. This stabilizes a wide range of bullet weights.
• Threads per Inch: 1/2×28. This is the standard thread pitch for 5.56 muzzle devices.
• Muzzle Device: Zeroed Linear Compensator. This directs sound forward, reducing perceived noise for the shooter.
• Material: Aluminum. This keeps the weight down while maintaining structural integrity.
• Gas Block Journal Size: .750 inch. This is a common size, making it compatible with many aftermarket gas blocks.
• Gun Rail: M-LOK. This provides ample attachment points for accessories.
• Gun Make: CMMG. This guarantees quality and innovation.
• Gun Model: CMMG Mk4. This ensures compatibility with standard AR-15 lowers.
• Magazine Included: No. This is standard for upper receivers.

These specifications translate to a highly maneuverable and capable platform. The short barrel and forward-projecting compensator are key to its function.

Performance & Functionality

The CMMG DISSENT Mk4, 5.56x45mm NATO, 6.5in Upper Receiver performs admirably for its size. Accuracy is acceptable out to 50 yards with proper sighting. The innovative direct impingement system offers reliable cycling.

The side-charging handle is a standout feature. It enables rapid reloads and malfunction clearances without breaking my sight picture. The DISSENT’s weaknesses are primarily inherent to its short barrel, namely increased muzzle flash and reduced ballistic performance compared to longer barrels. It performs as expected and offers something new.

Design & Ergonomics

The build quality of the CMMG DISSENT Mk4, 5.56x45mm NATO, 6.5in Upper Receiver is excellent. The aluminum feels durable and well-machined. Its weight is manageable, especially considering it houses the entire action.

The DISSENT is relatively user-friendly, although familiarization is needed due to the side-charging handle and bufferless design. The learning curve is minimal for experienced AR shooters.

Durability & Maintenance

Based on my experience, the CMMG DISSENT Mk4, 5.56x45mm NATO, 6.5in Upper Receiver is built to last. Routine cleaning and lubrication are all that’s required to maintain its functionality. I expect it to withstand thousands of rounds without issue.

Maintaining the DISSENT is similar to maintaining any direct impingement AR-15. No special tools or procedures are required.

Accessories and Customization Options

The CMMG DISSENT Mk4, 5.56x45mm NATO, 6.5in Upper Receiver readily accepts standard AR-15 accessories, except for those requiring a buffer tube. Optics, lights, and lasers can be easily mounted on the M-LOK handguard and Picatinny top rail.

The 1913 Picatinny rail end plate allows for attachment to a variety of braces, stocks (on SBR lowers), and folding mechanisms. This is a fantastic feature that provides significant flexibility. Compatibility with third-party accessories is broad.

Pros and Cons of CMMG DISSENT Mk4, 5.56x45mm NATO, 6.5in Upper Receiver

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Who Should Buy CMMG DISSENT Mk4, 5.56x45mm NATO, 6.5in Upper Receiver?

The CMMG DISSENT Mk4, 5.56x45mm NATO, 6.5in Upper Receiver is perfect for individuals seeking a highly concealable and maneuverable 5.56 platform. It is suitable for personal defense, truck guns, or anyone wanting a compact AR-style firearm. Those prioritizing maximum ballistic performance from a 5.56 should consider longer barrel options.

Someone new to AR-15 platforms might find the bufferless system slightly unusual at first. A quality brace or stock (depending on lower receiver configuration) and a reliable optic are must-have additions.

Conclusion on CMMG DISSENT Mk4, 5.56x45mm NATO, 6.5in Upper Receiver

The CMMG DISSENT Mk4, 5.56x45mm NATO, 6.5in Upper Receiver is a truly innovative piece of engineering. It packs the punch of a 5.56 into an unbelievably small package. The price is undoubtedly premium, but the innovative design and high-quality construction justify the cost for those prioritizing concealability and maneuverability.

I would absolutely recommend it to anyone looking for a top-tier compact AR-platform. If you’re seeking a cutting-edge firearm that defies convention, the CMMG DISSENT Mk4, 5.56x45mm NATO, 6.5in Upper Receiver is a worthwhile investment. Go experience the DISSENT for yourself and see what the future of compact ARs looks like.