The CMMG RESOLUTE MK4 UPPER GROUP .22 LR 17 Black Made a Bold First Impression
The CMMG RESOLUTE MK4 UPPER GROUP .22 LR 17 Black promises a seamless .22 LR conversion for any standard AR-15 lower, offering a cost-effective and versatile solution for training, plinking, and small-game hunting. CMMG has a solid reputation for quality AR components, and this upper group aims to deliver that same reliability in a rimfire package. I was searching for an affordable way to train with my AR platform without the expensive recoil and report of centerfire cartridges.
The promise of easy caliber conversion and the potential for inexpensive practice sessions were extremely appealing. The unit arrived well-packaged, and my initial impression was of robust construction. The black Cerakote finish looked durable and professional, and the included accessories felt solid. I considered a dedicated .22 LR AR-15 build, but the CMMG RESOLUTE MK4 UPPER GROUP .22 LR 17 Black offered the convenience of using my existing lower receiver.
I also briefly looked at the Tippmann Arms M4-22 and the Smith & Wesson M&P 15-22, both complete .22 LR rifles. Ultimately, the CMMG system won because it allows me to maintain the familiar ergonomics and controls of my primary AR-15. The CMMG RESOLUTE MK4 UPPER GROUP .22 LR 17 Black initially impressed me with its apparent quality and the promise of affordable training.
Real-World Testing: Putting CMMG RESOLUTE MK4 UPPER GROUP .22 LR 17 Black to the Test
First Use Experience
My first outing with the CMMG RESOLUTE MK4 UPPER GROUP .22 LR 17 Black was at my local outdoor shooting range. The weather was mild and sunny, perfect conditions for sighting in the new upper. Installation was straightforward, simply swapping out my existing upper receiver and securing it with the takedown pins. I was eager to see how it performed with various .22 LR ammunition types.
I experienced a few initial failures to feed with some bulk-pack ammunition, but switching to higher-quality CCI Mini-Mags seemed to resolve the issue. The blowback action was noticeably softer than my 5.56 NATO upper, making for a very comfortable shooting experience. Overall, the first range session showed potential, but it also revealed the need for careful ammunition selection.
Extended Use & Reliability
After several months of use, the CMMG RESOLUTE MK4 UPPER GROUP .22 LR 17 Black has proven to be a reliable training tool, though not without its quirks. I’ve put hundreds of rounds through it, mostly with CCI Mini-Mags and Aguila Super Extra, with significantly fewer malfunctions compared to the initial bulk-pack ammo. Cleaning is relatively simple; the bolt carrier group is easily disassembled and cleaned with standard solvents. The Cerakote finish has held up well with no signs of significant wear.
Compared to my experiences with dedicated .22 LR rifles, the CMMG upper requires more frequent cleaning to maintain optimal reliability. The CMMG RESOLUTE MK4 UPPER GROUP .22 LR 17 Black is a great addition to my training arsenal despite the need for select ammunition.
Breaking Down the Features of CMMG RESOLUTE MK4 UPPER GROUP .22 LR 17 Black
Specifications
Caliber: .22 LR – This allows for inexpensive training and practice. The .22 LR round is widely available and significantly cheaper than centerfire ammunition.
Barrel Length: 17 inches – The 17-inch barrel provides a good balance of accuracy and maneuverability. This length is suitable for various shooting applications, from target practice to small game hunting.
Barrel Twist: 1:16 – The 1:16 twist rate is optimized for stabilizing .22 LR bullets. This twist rate contributes to improved accuracy with a variety of .22 LR ammunition.
Barrel Material: 4140CM SBN – The 4140 Chrome Moly steel barrel offers good strength and durability. The Salt Bath Nitride (SBN) finish enhances corrosion resistance and extends barrel life.
Muzzle Device: CMMG ZEROED Muzzle Brake – The CMMG ZEROED muzzle brake is designed to reduce recoil and muzzle rise. While recoil is minimal with .22 LR, the muzzle brake adds a tactical appearance.
Upper Receiver: Billet 6061 T6 Aluminum – The billet 6061 T6 aluminum upper receiver provides a strong and lightweight platform. Billet construction ensures precise dimensions and enhanced durability.
Hand Guard: CMMG EML15 M-LOK – The CMMG EML15 M-LOK handguard offers ample space for attaching accessories. M-LOK slots provide a versatile mounting system for lights, lasers, and grips.
Charging Handle: CMMG ZEROED Ambi – The CMMG ZEROED ambidextrous charging handle allows for easy operation by both left- and right-handed shooters. The ambidextrous design enhances versatility and usability.
Weight: 4.0 lbs – The 4.0-pound weight of the upper group keeps the overall rifle relatively light. This weight is manageable for extended shooting sessions and various body types.
Performance & Functionality
The CMMG RESOLUTE MK4 UPPER GROUP .22 LR 17 Black performs admirably when paired with the right ammunition. Accuracy is acceptable for its intended purpose, providing tight groupings at 25-50 yards with quality ammo. It’s not a match-grade system, but perfectly adequate for plinking and training.
The blowback operation is reliable, but it’s crucial to use high-velocity ammunition for consistent cycling. Some lower-powered rounds may result in failures to eject. It would be ideal if CMMG included a guide on optimal ammunition selection.
Design & Ergonomics
The CMMG RESOLUTE MK4 UPPER GROUP .22 LR 17 Black boasts excellent build quality with a durable Cerakote finish. The weight is well-balanced, making it comfortable to shoot for extended periods. The M-LOK handguard provides a secure and comfortable grip.
The upper fits snugly on my AR-15 lower receiver, with no noticeable wobble or play. The ambidextrous charging handle is a welcome feature, allowing for easy manipulation from either side. The design is well-thought-out and user-friendly.
Durability & Maintenance
The 4140CM steel barrel and 6061 T6 aluminum upper receiver offer excellent durability. The Cerakote finish provides good corrosion resistance and helps protect against scratches and wear. Regular cleaning and lubrication are essential for maintaining smooth operation.
Disassembly for cleaning is straightforward, though the .22 LR cartridge tends to leave behind more fouling than centerfire rounds. A dedicated .22 LR cleaning kit is recommended. Overall, the CMMG RESOLUTE MK4 UPPER GROUP .22 LR 17 Black is built to last with proper care.
Accessories and Customization Options
The CMMG RESOLUTE MK4 UPPER GROUP .22 LR 17 Black comes with a CMMG ZEROED muzzle brake, a CMMG ZEROED ambidextrous charging handle, and a ZEROED AR15 Polymer Dust Cover. The M-LOK handguard allows for the attachment of various accessories, such as lights, lasers, and vertical grips. The upper is compatible with any standard AR-15 lower receiver and .22 LR conversion magazines.
I added a red dot sight for quicker target acquisition and a vertical grip for improved control. The modularity of the AR-15 platform allows for nearly endless customization options. I’ve found that CMMG magazines are the most reliable, but some aftermarket options also work well.
Pros and Cons of CMMG RESOLUTE MK4 UPPER GROUP .22 LR 17 Black
Pros
- Affordable training: Allows for inexpensive practice with the AR-15 platform.
- Easy conversion: Quickly converts any standard AR-15 lower to .22 LR.
- Durable construction: High-quality materials and Cerakote finish ensure longevity.
- M-LOK handguard: Provides ample space for attaching accessories.
- Ambidextrous charging handle: Accommodates both left- and right-handed shooters.
Cons
- Requires high-velocity ammunition for optimal reliability.
- Needs more frequent cleaning compared to centerfire uppers.
- Price is higher than some dedicated .22LR rifles.
Who Should Buy CMMG RESOLUTE MK4 UPPER GROUP .22 LR 17 Black?
Perfect for: AR-15 owners looking for a cost-effective training solution, shooting enthusiasts seeking a fun plinking experience, and small game hunters who want a lightweight and accurate rimfire option. It’s also a great choice for those who appreciate the modularity and familiarity of the AR-15 platform.
Who should skip this product? Shooters who primarily use low-powered .22 LR ammunition, those unwilling to invest in quality .22 LR magazines, or individuals seeking match-grade accuracy.
Must-have accessories or modifications? A reliable red dot sight, quality .22 LR magazines (preferably CMMG), and a dedicated .22 LR cleaning kit are essential.
Conclusion on CMMG RESOLUTE MK4 UPPER GROUP .22 LR 17 Black
The CMMG RESOLUTE MK4 UPPER GROUP .22 LR 17 Black is a solid investment for AR-15 owners seeking an affordable and versatile .22 LR conversion. While it requires specific ammunition and more frequent cleaning, the benefits of inexpensive training and familiar ergonomics outweigh the drawbacks. At $635.99, the price is justified by the quality of the components and the overall performance of the system.
I would definitely recommend the CMMG RESOLUTE MK4 UPPER GROUP .22 LR 17 Black to anyone looking to expand the capabilities of their AR-15. It’s a fun, reliable, and cost-effective way to enjoy the shooting sports. Consider adding it to your collection for accessible, budget-friendly enjoyment.