The CMMG RESOLUTE MK4 UPPER GROUP 6MM ARC 16.1 Black Made a Bold First Impression
The CMMG RESOLUTE MK4 UPPER GROUP 6MM ARC 16.1 Black arrives promising a potent blend of accuracy and manageable recoil, chambered in the increasingly popular 6mm ARC. As an experienced outdoorsman and tactical gear specialist, I’m always searching for equipment that bridges the gap between range performance and real-world applicability. The 6mm ARC cartridge, with its flatter trajectory and reduced wind drift compared to the 5.56 NATO, immediately piqued my interest for its potential in hunting and long-range target shooting.
For years, I’ve tinkered with AR-15 builds, constantly chasing the perfect balance of power and precision. I was specifically seeking a reliable and accurate upper receiver group that I could easily drop onto a standard AR-15 lower. The promise of CMMG’s quality and the 6mm ARC chambering sealed the deal.
Unboxing the CMMG RESOLUTE MK4 UPPER GROUP 6MM ARC 16.1 Black revealed a well-assembled unit. The black Cerakote finish exuded durability, and the components felt solid and well-made. The included ZEROED accessories, such as the ambi charging handle and muzzle brake, were welcome additions.
I considered options from Bravo Company Manufacturing (BCM) and Daniel Defense, both renowned for their AR-15 components. However, the 6mm ARC chambering and the complete upper group configuration of the CMMG offering made it the most appealing choice for my specific needs. The CMMG seemed a faster path to get the 6mm ARC performance that I wanted.
My first impression was one of cautious optimism. The CMMG RESOLUTE MK4 UPPER GROUP 6MM ARC 16.1 Black appeared to be a well-engineered product, but the true test would be its performance on the range and in the field.
Real-World Testing: Putting CMMG RESOLUTE MK4 UPPER GROUP 6MM ARC 16.1 Black to the Test
First Use Experience
My first outing with the CMMG RESOLUTE MK4 UPPER GROUP 6MM ARC 16.1 Black was at my local shooting range. The weather was clear and calm, providing ideal conditions for zeroing the optic and testing the accuracy of the upper. I paired it with a trusted AR-15 lower that I’ve used for years.
The CMMG RESOLUTE MK4 UPPER GROUP 6MM ARC 16.1 Black felt comfortable and familiar in my hands. The rifle-length gas system seemed to contribute to a smoother recoil impulse than other ARs I have shot. I was able to quickly and easily get it zeroed.
The only minor issue I encountered during this first session was related to magazine compatibility with my lower. Some magazines did not feed as reliably with the 6mm ARC as they do with standard 5.56 ammunition, which is something to keep in mind when first getting into 6mm ARC.
Extended Use & Reliability
After several months of regular use, the CMMG RESOLUTE MK4 UPPER GROUP 6MM ARC 16.1 Black has proven to be a reliable and accurate platform. I’ve used it in a variety of conditions, from sunny range days to a dusty coyote hunting trip. It has always performed without issue.
The CMMG’s black Cerakote finish has held up admirably, showing minimal signs of wear despite being bumped around in trucks and against shooting barricades. Cleaning is straightforward, with no unusual nooks or crannies to worry about. Standard AR-15 cleaning procedures work just fine.
In comparison to previous AR-15 builds I’ve experimented with, the CMMG RESOLUTE MK4 UPPER GROUP 6MM ARC 16.1 Black delivers superior accuracy and a noticeably flatter trajectory, making it easier to engage targets at longer distances. It has lived up to my expectations and then some.
Breaking Down the Features of CMMG RESOLUTE MK4 UPPER GROUP 6MM ARC 16.1 Black
Specifications
Caliber: 6mm ARC. This cartridge offers a significant ballistic advantage over the 5.56 NATO, with a flatter trajectory and improved resistance to wind drift.
Barrel Length: 16.1 inches. This provides a good balance between maneuverability and ballistic performance, making it suitable for a variety of applications.
Barrel Twist: 1:7.5 inches. This twist rate is optimized for stabilizing the longer, heavier bullets typically used in 6mm ARC.
Barrel Material: 416SS SBN. The 416 stainless steel provides excellent corrosion resistance, and the Salt Bath Nitride (SBN) treatment further enhances durability and reduces friction.
Muzzle Device: CMMG ZEROED Muzzle Brake. This helps to reduce felt recoil and muzzle rise, allowing for faster follow-up shots.
Upper Receiver: Billet 6061 T6 Aluminum. Billet receivers are stronger and more rigid than forged receivers, contributing to improved accuracy.
Hand Guard: CMMG EML15 M-LOK. The 15-inch handguard provides ample space for mounting accessories, and the M-LOK slots offer a versatile attachment system.
Weight: 4.3 lbs. This is a reasonable weight for a complete upper group, making it easy to handle and maneuver.
Length: 25 inches. This length allows for good stability while still being compact.
Gas Port Location: Rifle. Rifle-length gas systems generally provide a smoother recoil impulse compared to carbine-length or mid-length systems.
Gas Block: 0.750 Non-Adjustable. A reliable and durable gas block ensures consistent cycling.
Charging Handle: CMMG ZEROED Ambi. The ambidextrous design makes it easier to operate the charging handle from either side of the rifle.
Finish: Cerakote Standard. The Cerakote finish provides excellent corrosion resistance and a durable, attractive appearance.
Performance & Functionality
The CMMG RESOLUTE MK4 UPPER GROUP 6MM ARC 16.1 Black performs exceptionally well in terms of accuracy, reliability, and usability. Its accuracy is outstanding. I am regularly achieving sub-MOA groups at 100 yards.
The only slight weakness is the magazine compatibility, which isn’t necessarily a fault of the upper itself, but rather a characteristic of the 6mm ARC cartridge. It definitely meets and exceeds expectations. The performance has been more than what I was hoping for.
Design & Ergonomics
The build quality is excellent, with high-quality materials and precise machining. The weight is manageable, and the ergonomics are comfortable. It is a user-friendly design with a very short learning curve. Most AR-15 users will feel right at home with it.
Durability & Maintenance
Given the high-quality materials and robust construction, I expect the CMMG RESOLUTE MK4 UPPER GROUP 6MM ARC 16.1 Black to last for many years with proper care. Cleaning is easy, and no special tools are required.
Accessories and Customization Options
The CMMG RESOLUTE MK4 UPPER GROUP 6MM ARC 16.1 Black comes with the ZEROED AR15 Polymer Dust Cover, ZEROED AR15 Ambi Charging Handle, and ZEROED Muzzle Brake 6.5mm. The M-LOK handguard provides plenty of real estate for mounting optics, lights, lasers, and other accessories. It is compatible with any standard AR-15 lower receiver. The muzzle thread is 5/8 x 24, making it compatible with a wide range of muzzle devices.
Pros and Cons of CMMG RESOLUTE MK4 UPPER GROUP 6MM ARC 16.1 Black
Pros
- Exceptional Accuracy: Consistently delivers sub-MOA groups, making it ideal for precision shooting and hunting.
- Flatter Trajectory: The 6mm ARC cartridge offers a significantly flatter trajectory compared to 5.56 NATO, improving long-range performance.
- High-Quality Components: Features a billet upper receiver, 416SS barrel, and ZEROED accessories, ensuring durability and reliability.
- Smooth Recoil Impulse: The rifle-length gas system and muzzle brake combine to reduce felt recoil, making it comfortable to shoot for extended periods.
- Easy to Install: Drops onto any standard AR-15 lower receiver, making it a simple upgrade.
Cons
- Magazine Compatibility: May require specific magazines designed for 6mm ARC to ensure reliable feeding.
- Ammunition Availability: 6mm ARC ammunition is less widely available and typically more expensive than 5.56 NATO.
Who Should Buy CMMG RESOLUTE MK4 UPPER GROUP 6MM ARC 16.1 Black?
The CMMG RESOLUTE MK4 UPPER GROUP 6MM ARC 16.1 Black is perfect for hunters seeking a flat-shooting, accurate cartridge for medium-sized game. It is also ideal for competitive shooters who demand the highest levels of accuracy and long-range performance. Long-range target shooters will also find value.
This product might not be the best choice for those on a tight budget or those who prioritize readily available and inexpensive ammunition. If your primary concern is having a firearm that can shoot 5.56 NATO or .223, and you do not need the performance increase provided by 6mm ARC, then this would not be the best option.
A must-have accessory would be high-quality magazines specifically designed for 6mm ARC. Also, a quality optic with appropriate magnification for long-range shooting is also highly recommended.
Conclusion on CMMG RESOLUTE MK4 UPPER GROUP 6MM ARC 16.1 Black
The CMMG RESOLUTE MK4 UPPER GROUP 6MM ARC 16.1 Black is an outstanding product that delivers exceptional accuracy, reliability, and performance. The price is justified by the quality of the components and the significant ballistic advantages offered by the 6mm ARC cartridge.
I would personally recommend the CMMG RESOLUTE MK4 UPPER GROUP 6MM ARC 16.1 Black to anyone looking for a high-performance AR-15 upper receiver. It is an investment that will pay off with improved accuracy and long-range capability. If you want to take your AR-15 to the next level, this is the way to do it.