CMMG Mk4 Endeavor Upper Receiver Group Review

Let’s Talk CMMG Mk4 Endeavor Upper Receiver Group

The CMMG Mk4 Endeavor Upper Receiver Group is a complete upper receiver assembly designed to enhance the performance and range of your existing AR-15 lower. Manufactured by CMMG, a reputable name in the AR platform world, this upper boasts an 18-inch 416 stainless steel barrel, a rifle-length gas system, and an M-LOK handguard. This configuration promises improved accuracy and reliability, making it a tempting upgrade for any AR-15 enthusiast.

I was looking to extend the effective range of my go-to AR-15 without building a completely new rifle. I needed an upper that would deliver consistent accuracy at longer distances while maintaining the AR-15’s familiar ergonomics and modularity.

Unboxing the CMMG Mk4 Endeavor Upper Receiver Group, I was immediately struck by the quality of the finish and the solid feel of the components. The Armor Black coating looked durable and evenly applied, and the handguard felt robust and well-machined. The weight felt balanced and appropriate for an 18-inch barrel.

I was considering a similar upper from Bravo Company Manufacturing (BCM) and a complete upper from Palmetto State Armory (PSA). I chose the CMMG Mk4 Endeavor Upper Receiver Group for its combination of stainless steel barrel, rifle-length gas system, and CMMG’s reputation for quality control. The other options seemed to cut corners in one area or another.

My first impression was overwhelmingly positive. The upper looked and felt like a significant upgrade, and I was eager to see how it performed on the range. I was excited!

Real-World Testing: Putting CMMG Mk4 Endeavor Upper Receiver Group to the Test

First Use Experience

I tested the CMMG Mk4 Endeavor Upper Receiver Group at my local outdoor range, which offers distances out to 300 yards. The weather was clear and sunny, with a slight breeze – ideal conditions for sighting in a new upper. I used a variety of 5.56mm ammunition, ranging from standard 55-grain FMJ to heavier 77-grain match rounds.

The CMMG Mk4 Endeavor Upper Receiver Group performed flawlessly. The rifle-length gas system provided smooth and consistent cycling, and the recoil felt noticeably softer compared to my 16-inch carbine. It was very easy to get used to. The longer sight radius improved my accuracy, and I was quickly hitting targets at 200 and 300 yards with surprising ease.

After the first 50 rounds, I noticed that the CMMG Zeroed Muzzle Brake did a fantastic job of mitigating recoil and muzzle rise. This allowed for faster follow-up shots.

Extended Use & Reliability

After several months of regular use, the CMMG Mk4 Endeavor Upper Receiver Group has continued to impress. It has proven to be exceptionally reliable. It has digested hundreds of rounds without a single malfunction, regardless of the ammunition used.

The Armor Black finish has held up well, with only minor signs of wear and tear in high-contact areas. Cleaning and maintenance are straightforward. The stainless steel barrel wipes down easily, and the M-LOK handguard provides ample access for cleaning the gas system.

Compared to my previous experiences with shorter, carbine-length uppers, the CMMG Mk4 Endeavor Upper Receiver Group is a significant step up in terms of accuracy and shootability. It outperforms my expectations.

Breaking Down the Features of CMMG Mk4 Endeavor Upper Receiver Group

Specifications

• Caliber: 5.56x45mm NATO. This is the standard AR-15 caliber, offering a wide range of ammunition options.
• Overall Length: 26.9 inches. Provides a longer sight radius and improved ballistic performance.
• Barrel Length: 18 inches. Optimizes velocity and accuracy for longer-range shooting.
• Barrel Profile: Medium Taper. Strikes a balance between weight and rigidity for enhanced accuracy.
• Gas System Length: Rifle Length. Reduces recoil and increases reliability compared to shorter gas systems.
• Barrel Twist Rate: 1-7. Stabilizes heavier bullets for improved long-range performance.
• Threads per Inch: 1/2×28. Compatible with a wide range of muzzle devices.
• Muzzle Device: CMMG Zeroed Muzzle Brake. Effectively reduces recoil and muzzle rise.
• Color: Armor Black. Provides a durable and corrosion-resistant finish.
• Fabric/Material: 416SS. Offers excellent corrosion resistance and heat dissipation.
• Gas Block Journal Size-Diameter: .750 inch. A common size, allowing for aftermarket gas block options.
• Gun Rail: M-LOK. Provides a modular and lightweight platform for attaching accessories.
• Gun Type: Rifle. Designed for use with AR-15 platform rifles.
• Gun Make: CMMG. Ensures high-quality manufacturing and reliable performance.
• Gun Model: CMMG Mk4. Specifies the AR-15 pattern compatibility.
• Weight: 4.5 lb. Adds some weight but helps to mitigate recoil.
• Condition: New. Guarantees that you are receiving a brand-new, unused product.
• Magazine Included: No. Allows you to use your existing AR-15 magazines.
• Mount Type: M-LOK. Enables the easy attachment of accessories along the rail.

Performance & Functionality

The CMMG Mk4 Endeavor Upper Receiver Group excels in delivering enhanced accuracy and reliable performance. The longer barrel and rifle-length gas system work in harmony to provide a smoother shooting experience with improved ballistic capabilities. It exceeded expectations in terms of both accuracy and reliability.

A notable strength is the enhanced accuracy at longer ranges, making it ideal for target shooting and hunting. A potential weakness is that the 18-inch barrel may not be ideal for close-quarters combat.

It meets expectations and in some cases, exceeds them.

Design & Ergonomics

The CMMG Mk4 Endeavor Upper Receiver Group features a well-thought-out design with high-quality materials. The 416 stainless steel barrel ensures durability and consistent performance, while the M-LOK handguard offers a comfortable and customizable platform. The weight is balanced well.

The upper is user-friendly, requiring no special tools or expertise to install on a compatible AR-15 lower receiver. There is no learning curve.

Durability & Maintenance

The robust construction and durable Armor Black finish suggest that the CMMG Mk4 Endeavor Upper Receiver Group is built to last. With proper care and maintenance, it should provide years of reliable service.

The stainless steel barrel is easy to clean, and the M-LOK handguard provides easy access to the gas system for maintenance. Very easy to maintain.

Accessories and Customization Options

The CMMG Mk4 Endeavor Upper Receiver Group comes with a CMMG Zeroed Muzzle Brake, which is a good starting point. The M-LOK handguard provides ample space for attaching accessories such as optics, lights, and foregrips.

The upper is compatible with most standard AR-15 accessories, allowing for a high degree of customization. Adding a quality optic and a comfortable sling would be highly recommended.

Pros and Cons of CMMG Mk4 Endeavor Upper Receiver Group

Who Should Buy CMMG Mk4 Endeavor Upper Receiver Group?

Perfect for: Target shooters looking for enhanced accuracy, hunters needing extended range, and AR-15 enthusiasts seeking a high-quality upgrade. This is also great for anyone who wants to improve their existing setup without the expense of buying a completely new rifle.

Who should skip this product? Those primarily focused on close-quarters combat or those prioritizing ultra-lightweight builds.

Must-have accessories or modifications? A quality optic (red dot or scope) to take advantage of the increased accuracy, a comfortable sling, and possibly an upgraded trigger in the lower receiver.

Conclusion on CMMG Mk4 Endeavor Upper Receiver Group

The CMMG Mk4 Endeavor Upper Receiver Group is a worthwhile upgrade for anyone looking to enhance the performance and extend the range of their AR-15. Its combination of high-quality components, reliable performance, and modular design make it a standout option in its price range. The price of $806.67 is justified by the quality and performance.

I would personally recommend it to anyone looking for a reliable and accurate AR-15 upper receiver group. If you’re ready to take your AR-15 to the next level, the CMMG Mk4 Endeavor Upper Receiver Group is an excellent choice. Invest in your accuracy and upgrade today!