CMMG RESOLUTE MK4 UPPER GROUP 6.5GREN 16.1 Black Review

The CMMG RESOLUTE MK4 UPPER GROUP 6.5GREN 16.1 Black Made a Bold First Impression

The CMMG RESOLUTE MK4 UPPER GROUP 6.5GREN 16.1 Black isn’t just another AR-15 upper; it’s a statement. It promises flat shooting at longer distances, utilizing the efficient ballistics of the 6.5 Grendel cartridge. This complete upper receiver assembly from CMMG arrives ready to drop onto any standard AR-15 lower, immediately upgrading its capabilities.

I was looking for a way to extend my effective range without sacrificing the familiar AR platform. I wanted to reach out past 5.56 NATO’s limitations and touch targets with more authority. The 6.5 Grendel’s reputation for accuracy and retained energy at distance drew me in, and the CMMG RESOLUTE MK4 seemed like a well-engineered solution.

The upper arrived well-packaged, and my first impression was positive. The black Cerakote finish looked flawless, and the overall fit and finish were excellent. It felt solid and well-built without being excessively heavy.

I considered building a custom upper but ultimately chose the CMMG for its reputation for quality control and the inclusion of ZEROED accessories. Compared to a similar upper from Bravo Company Manufacturing (BCM), the CMMG offered the 6.5 Grendel chambering I wanted. It seemed a more complete package than a comparable offering from Aero Precision. I was definitely excited to get it to the range.

Real-World Testing: Putting CMMG RESOLUTE MK4 UPPER GROUP 6.5GREN 16.1 Black to the Test

First Use Experience

I took the CMMG RESOLUTE MK4 UPPER GROUP 6.5GREN 16.1 Black to my local shooting range, which has distances out to 300 yards. The weather was clear, with a slight crosswind. I mounted a Vortex Strike Eagle 1-8×24 scope and used a bipod for stability.

I immediately noticed the reduced recoil compared to my 5.56 AR. The 6.5 Grendel felt smooth and controllable. The ZEROED Muzzle Brake did a good job of mitigating recoil, and the rifle stayed on target well.

There were no malfunctions during the first 100 rounds, and the upper ran flawlessly. Initial groupings at 100 yards were promising, hovering around 1 MOA with Hornady Black 123gr ELD Match ammunition. I was very pleased with the initial results and excited to stretch the CMMG’s legs.

Extended Use & Reliability

After several months of use, including multiple range trips and a weekend hunting trip, the CMMG RESOLUTE MK4 UPPER GROUP 6.5GREN 16.1 Black continues to impress. I’ve put several hundred rounds through it with no issues. Cleaning is straightforward, and the 416SS SBN barrel cleans up easily.

There are no noticeable signs of wear and tear beyond some minor finish wear on the charging handle. I’ve primarily used it with Hornady and Alexander Arms ammunition. It consistently delivers sub-MOA accuracy.

Compared to my old 5.56 upper, the CMMG provides significantly better long-range performance and terminal ballistics. This allows for ethical shots on game at greater distances. The CMMG RESOLUTE MK4 has exceeded my expectations.

Breaking Down the Features of CMMG RESOLUTE MK4 UPPER GROUP 6.5GREN 16.1 Black

Specifications

• Caliber: 6.5 Grendel. This cartridge provides superior ballistic performance compared to 5.56 NATO, offering flatter trajectories and better energy retention at longer ranges.
• Barrel Length: 16.1 inches. This length strikes a good balance between maneuverability and velocity. It allows the 6.5 Grendel to reach its full potential.
• Barrel Twist: 1:8. This twist rate is optimal for stabilizing the common 6.5mm bullet weights, ensuring accuracy.
• Barrel Contour: MT (Medium Taper). The MT contour provides a good balance between weight and rigidity for consistent accuracy.
• Barrel Material: 416SS SBN (Salt Bath Nitride). 416 stainless steel offers excellent corrosion resistance. The SBN treatment further enhances durability and reduces friction.
• Muzzle Device: CMMG ZEROED Muzzle Brake. This brake effectively reduces recoil, allowing for faster follow-up shots.
• Gas Port Location: Rifle. Rifle-length gas systems provide a smoother recoil impulse compared to shorter gas systems.
• Gas Block: 0.750 Non-Adjustable. The standard size gas block is reliable and simple.
• Upper Receiver: Billet 6061 T6 Aluminum. The billet construction adds strength and rigidity.
• Hand Guard: CMMG EML15 M-LOK. The 15-inch handguard provides ample space for accessories. The M-LOK slots offer versatile mounting options.
• Charging Handle: CMMG ZEROED Ambi. The ambidextrous charging handle is a welcome feature for left-handed shooters or those who prefer alternative charging methods.
• Weight: 4.3 lbs. The weight is reasonable for a complete upper receiver group.
• Length: 25 inches. This is the overall length of the upper receiver assembly.

Performance & Functionality

The CMMG RESOLUTE MK4 UPPER GROUP 6.5GREN 16.1 Black performs exceptionally well. It consistently delivers sub-MOA accuracy with quality ammunition. The rifle-length gas system and effective muzzle brake make it comfortable to shoot.

Its greatest strength is its long-range capability compared to a standard AR-15. The accuracy and retained energy are impressive. A minor weakness might be the non-adjustable gas block, which could limit its ability to function optimally with a wide range of ammunition.

It met and, in some areas, exceeded my expectations, especially in terms of accuracy.

Design & Ergonomics

The build quality is excellent, with tight tolerances and a durable finish. The CMMG EML15 M-LOK handguard is comfortable to grip and provides plenty of space for accessories. The overall weight is manageable.

The upper is user-friendly and requires no special tools or modifications to install on a standard AR-15 lower. The ZEROED Ambi Charging Handle is a nice touch and improves usability.

Durability & Maintenance

The use of 416SS SBN for the barrel indicates long-term durability. The Cerakote finish is also durable and resists scratches and wear. With proper maintenance, this upper should last for many years.

Maintenance is straightforward, similar to any other AR-15. Regular cleaning and lubrication are all that’s required.

Accessories and Customization Options

The CMMG RESOLUTE MK4 UPPER GROUP 6.5GREN 16.1 Black comes with the ZEROED AR15 Polymer Dust Cover, ZEROED AR15 Ambi Charging Handle, and ZEROED Muzzle Brake 6.5mm. The EML15 M-LOK handguard provides ample space for attaching lights, lasers, and other accessories.

It’s compatible with any standard AR-15 lower receiver and magazines designed for 6.5 Grendel. Optics are easily mounted on the Picatinny rail of the upper receiver. The M-LOK slots also allow for mounting bipods and other accessories directly to the handguard.

Pros and Cons of CMMG RESOLUTE MK4 UPPER GROUP 6.5GREN 16.1 Black

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Who Should Buy CMMG RESOLUTE MK4 UPPER GROUP 6.5GREN 16.1 Black?

Perfect for: Hunters looking for increased range and terminal ballistics, competitive shooters needing a flat-shooting and accurate rifle, and anyone wanting to upgrade their AR-15 to the versatile 6.5 Grendel cartridge.

Who should skip this product? Those on a very tight budget or those who primarily shoot at very close ranges.

Must-have accessories or modifications? A quality optic is essential to take advantage of the CMMG’s accuracy potential. A good bipod or shooting rest is also recommended for precision shooting.

Conclusion on CMMG RESOLUTE MK4 UPPER GROUP 6.5GREN 16.1 Black

The CMMG RESOLUTE MK4 UPPER GROUP 6.5GREN 16.1 Black is a high-quality, accurate, and reliable upper receiver group that significantly enhances the capabilities of any standard AR-15. The price is justified by the superior components, included accessories, and excellent performance.

I would personally recommend the CMMG RESOLUTE MK4 UPPER GROUP 6.5GREN 16.1 Black to anyone looking to upgrade to the 6.5 Grendel cartridge. It’s a worthwhile investment that will provide years of accurate and reliable service. If you’re ready to extend your range and increase your AR’s effectiveness, seriously consider this upper!

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