CMMG DISSENT Mk4, 300BLK, 14.5in P&W Upper Receiver Review

First Impressions of CMMG DISSENT Mk4, 300BLK, 14.5in P&W Upper Receiver

The CMMG DISSENT Mk4, 300BLK, 14.5in P&W Upper Receiver is a groundbreaking piece of engineering that promises to redefine the AR pistol and short-barreled rifle landscape. Manufactured by CMMG, this upper receiver boasts a bufferless design, a non-reciprocating side charging handle, and a pinned and welded muzzle brake to achieve a non-NFA overall length. The promise of AR-15 ergonomics in a compact, easily maneuverable package is undeniably alluring.

My journey to this particular upper started with a need for a compact, yet ballistically effective, home defense weapon. I wanted something shorter and handier than a traditional AR, but I wasn’t willing to sacrifice the proven reliability and modularity of the AR platform. I also have an interest in .300 Blackout for its versatility in both subsonic and supersonic loads.

Upon unboxing the CMMG DISSENT Mk4, 300BLK, 14.5in P&W Upper Receiver, the first thing I noticed was its robust build quality. The Cerakote finish (I opted for Midnight Bronze) was flawless, and the fit and finish were impeccable. It felt solid in my hands, reassuringly heavy without being cumbersome; a tangible indication of the quality components inside.

I was torn between the CMMG DISSENT and similar offerings like the Maxim Defense PDX and the Q Honey Badger, both known for their compact size and innovative designs. I ultimately chose the CMMG due to its direct impingement system, which I believe offers a more reliable and predictable recoil impulse than the piston systems found in some competitors. The AR-15 familiarity also played a role.

My initial reaction was one of excited anticipation. The CMMG DISSENT held the promise of being the perfect blend of AR-15 functionality and compact maneuverability I’d been seeking. I couldn’t wait to get it to the range and put it through its paces.

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Real-World Testing: Putting CMMG DISSENT Mk4, 300BLK, 14.5in P&W Upper Receiver to the Test

First Use Experience

My initial testing took place at my local outdoor shooting range. I paired the CMMG DISSENT Mk4, 300BLK, 14.5in P&W Upper Receiver with a dedicated AR-15 lower receiver that I had already fitted with a high-quality trigger and a pistol brace. The weather was dry and mild, around 70 degrees Fahrenheit, providing ideal conditions.

The first few magazines were a mix of supersonic and subsonic .300 Blackout ammunition. The CMMG DISSENT cycled both flawlessly, exhibiting consistent ejection patterns and minimal felt recoil. The side charging handle was intuitive and smooth to operate, allowing for quick reloads and malfunction clearing without breaking my cheek weld.

There were no immediate issues or surprises. The CMMG DISSENT functioned exactly as advertised, providing a smooth and controllable shooting experience. I found the ergonomics of the side charging handle and the overall balance of the firearm to be excellent.

Extended Use & Reliability

After several months of regular use, the CMMG DISSENT Mk4, 300BLK, 14.5in P&W Upper Receiver has proven to be exceptionally reliable. I’ve put hundreds of rounds through it, ranging from cheap bulk ammo to premium self-defense rounds, without a single malfunction. The CMMG has become one of my favorite range toys.

The Cerakote finish has held up remarkably well, showing no signs of wear or scratches, even after being subjected to rough handling in the field. Regular cleaning and lubrication are all it takes to keep the CMMG DISSENT running smoothly. The bolt carrier group wipes clean with minimal effort.

Compared to my previous AR-15 pistols, the CMMG DISSENT is a clear winner in terms of size, weight, and overall maneuverability. Its bufferless design allows for a much shorter overall length, making it ideal for use in tight spaces, such as inside a vehicle or in a home defense scenario. It certainly outperforms my previous short barreled builds.

Breaking Down the Features of CMMG DISSENT Mk4, 300BLK, 14.5in P&W Upper Receiver

Specifications

• Caliber: .300 AAC Blackout provides flexibility for subsonic suppressed use and supersonic performance. The .300 BLK round is a great option for a wide range of applications.
• Overall Length: 23.6 inches makes it compact for storage and maneuverability. This short overall length is due to the bufferless design.
• Barrel Length: 14.5 inches offers a good balance between ballistics and compactness. The pinned and welded muzzle brake brings the total barrel length to over 16 inches.
• Barrel Twist Rate: 1-7 stabilizes a wide range of .300 Blackout bullet weights. This twist rate is optimal for both supersonic and subsonic rounds.
• Threads per Inch: 5/8×24 is a common .300 Blackout muzzle thread pattern. It allows for the use of many aftermarket muzzle devices and suppressors.
• Muzzle Device: CMMG Zeroed Muzzle Brake reduces recoil and muzzle rise. The pinning and welding makes this a permanent modification.
• Fabric/Material: Aluminum keeps the weight down while maintaining strength. Aluminum is the standard for most AR-15 upper receivers.
• Gas Block Journal Size-Diameter: .750 in is a common size for AR-15 gas blocks. This makes it easier to find aftermarket gas blocks if desired.
• Gun Rail: M-LOK allows for easy attachment of accessories. M-LOK provides a streamlined and secure attachment method.
• Weight: 4 lb is relatively lightweight for a complete upper receiver. The weight is low considering the 14.5 inch barrel and attached muzzle brake.
• Magazine Included: No means you will need to supply your own magazines. AR-15 magazines are readily available and inexpensive.

Performance & Functionality

The CMMG DISSENT Mk4, 300BLK, 14.5in P&W Upper Receiver performs exceptionally well in its intended role as a compact, reliable, and accurate AR-15 upper receiver. Its bufferless design and side charging handle contribute to a smoother and more intuitive shooting experience. The CMMG is an exceptionally reliable platform.

Its strengths lie in its compact size, smooth operation, and reliable cycling of both supersonic and subsonic ammunition. A potential weakness is the proprietary nature of the action, which may limit aftermarket parts availability compared to standard AR-15 components. I am hoping aftermarket support grows with the popularity of this platform.

The CMMG DISSENT has exceeded my expectations. It provides the reliability and modularity of an AR-15 in a significantly smaller and more maneuverable package. It makes a great home defense or truck gun.

Design & Ergonomics

The build quality of the CMMG DISSENT Mk4, 300BLK, 14.5in P&W Upper Receiver is excellent. The Aluminum construction feels solid and durable, and the Cerakote finish provides a smooth and protective coating. The weight is well-balanced, making the firearm comfortable to hold and shoot.

The CMMG DISSENT is surprisingly user-friendly. The side charging handle is easy to reach and operate, and the M-LOK rail system provides ample space for mounting accessories. The recoil impulse is manageable even with supersonic ammunition.

Durability & Maintenance

The CMMG DISSENT Mk4, 300BLK, 14.5in P&W Upper Receiver appears to be built to last. The robust construction and high-quality materials suggest that it will withstand years of use. Regular cleaning and lubrication are all that’s required to keep it in good working order.

Disassembly for cleaning is relatively straightforward, although it requires a bit more attention than a standard AR-15 due to the compact action. The bolt carrier group can be removed and cleaned with standard AR-15 cleaning tools. Replacement parts can be ordered directly from CMMG.

Accessories and Customization Options

The CMMG DISSENT Mk4, 300BLK, 14.5in P&W Upper Receiver includes a lower receiver end plate and a choice of adapter (1913 Picatinny rail, buffer tube adapter, or DISSENT folding stock). This allows users to customize their pistol or SBR with their preferred stock or brace. The side charging handle can be swapped to the right side with an optional charging handle.

The M-LOK rail system provides ample space for mounting accessories such as lights, lasers, and vertical grips. The CMMG DISSENT is also compatible with most AR-15 magazines and triggers. I like that it is easy to add accessories.

Pros and Cons of CMMG DISSENT Mk4, 300BLK, 14.5in P&W Upper Receiver

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Who Should Buy CMMG DISSENT Mk4, 300BLK, 14.5in P&W Upper Receiver?

The CMMG DISSENT Mk4, 300BLK, 14.5in P&W Upper Receiver is perfect for individuals seeking a compact, reliable, and accurate AR-15 pistol or SBR. It excels in home defense, vehicle carry, and other situations where maneuverability is paramount. It is a great option for .300 Blackout enthusiasts.

Those who prioritize affordability and extensive aftermarket support may want to consider a standard AR-15 upper receiver. Anyone who is not comfortable with more involved disassembly and cleaning procedures may also want to look elsewhere. This upper is more complex than a standard AR upper.

Must-have accessories include a high-quality pistol brace or stock, a reliable optic, and a weapon light. A suppressor is also highly recommended for those planning to use subsonic ammunition. I also recommend purchasing a few extra magazines.

Conclusion on CMMG DISSENT Mk4, 300BLK, 14.5in P&W Upper Receiver

The CMMG DISSENT Mk4, 300BLK, 14.5in P&W Upper Receiver is a truly innovative and well-executed firearm component. Its bufferless design, smooth operation, and reliable cycling make it a standout performer in the AR pistol and SBR market.

While the price point is higher than standard AR-15 upper receivers, the added benefits of compactness and maneuverability justify the cost for those who prioritize these features. The proprietary nature of the action is a minor drawback. I think this upper is well worth the price.

I wholeheartedly recommend the CMMG DISSENT Mk4, 300BLK, 14.5in P&W Upper Receiver to anyone seeking a compact, reliable, and accurate AR-15 pistol or SBR. If you are looking for an AR pistol or SBR, I recommend purchasing this upper. Experience the future of the AR platform for yourself.