First Impressions of CMMG Mk4/AR15 Upper Receiver Assembly w/Forward Assist
The AR-15 platform is the Lego set of the firearms world, offering endless customization options. When starting a new build, the upper receiver is a crucial component, and the CMMG Mk4/AR15 Upper Receiver Assembly w/Forward Assist presents a solid foundation. CMMG is a well-regarded manufacturer known for quality AR components, and this upper receiver assembly is designed to be a reliable workhorse.
My latest project was to build a lightweight, general-purpose AR-15 for range training and potential home defense. I needed an upper receiver that was durable, mil-spec compatible, and readily available. The CMMG Mk4/AR15 Upper Receiver Assembly w/Forward Assist ticked all those boxes, plus it was offered at a competitive price point.
The unit arrived well-packaged. My initial impression was positive: the finish was clean and even, and the receiver felt solid in hand. The forward assist moved smoothly, and the overall build quality seemed excellent for the price.
I considered upper receivers from Aero Precision and Bravo Company Manufacturing (BCM). While Aero Precision offers similar value, I wanted a more established brand, and BCM was outside my budget for this build. The CMMG Mk4/AR15 Upper Receiver Assembly w/Forward Assist seemed like the perfect balance of quality and affordability. I was excited to start building.
Real-World Testing: Putting CMMG Mk4/AR15 Upper Receiver Assembly w/Forward Assist to the Test
First Use Experience
I tested the CMMG Mk4/AR15 Upper Receiver Assembly w/Forward Assist at my local outdoor shooting range. I paired it with a CMMG 16″ barrel, a bolt carrier group from a reputable manufacturer, and a free-floating handguard. The initial testing involved firing approximately 200 rounds of .223 Remington and 5.56 NATO ammunition.
The upper receiver functioned flawlessly. There were no issues with feeding, extraction, or ejection. I experienced no malfunctions during this initial range session, even when rapidly firing multiple magazines.
The weather was clear and dry during my first range trip. It didn’t offer any real challenges to the equipment. The forward assist wasn’t needed during that session, a good sign indicating proper functioning of the BCG and ammunition.
Extended Use & Reliability
After several months of use, the CMMG Mk4/AR15 Upper Receiver Assembly w/Forward Assist has proven to be a dependable component. I’ve put approximately 1000 rounds through the completed rifle with this upper, including a mix of brass and steel-cased ammunition. The unit continues to perform reliably.
There are no signs of significant wear and tear. The Cerakote finish (I opted for the black version) has held up well with only minor scratches near the ejection port. Cleaning is straightforward; a simple wipe-down with a CLP-soaked cloth is sufficient after each range session.
I previously used a different upper receiver from a less-known brand. The CMMG upper receiver provides a noticeably tighter fit with various lower receivers, resulting in a more solid feel and potentially improved accuracy. The CMMG Mk4/AR15 Upper Receiver Assembly w/Forward Assist has exceeded my expectations, proving itself to be a worthwhile investment.
Breaking Down the Features of CMMG Mk4/AR15 Upper Receiver Assembly w/Forward Assist
Specifications
The CMMG Mk4/AR15 Upper Receiver Assembly w/Forward Assist is constructed from 7075-T6 aluminum, a durable and lightweight material commonly used in AR-15 receivers. It’s a mil-spec upper receiver, meaning it adheres to the dimensions and specifications outlined by the U.S. military. This ensures compatibility with a wide range of AR-15 parts and accessories.
The upper receiver features a standard M4 barrel extension cut. This allows for easy installation of most AR-15 barrels. It also includes a forward assist, a feature that allows the user to manually force the bolt carrier group into battery. Some argue this is a critical feature for reliability, especially in adverse conditions.
The unit is available in several Cerakote finishes. This provides enhanced corrosion resistance and a visually appealing aesthetic. The specifications also state that no magazine is included, as this is solely an upper receiver assembly. Users will need to source their own magazines separately.
Performance & Functionality
The CMMG Mk4/AR15 Upper Receiver Assembly w/Forward Assist performs its job admirably. It provides a stable and reliable platform for the bolt carrier group and barrel. The inclusion of the forward assist offers peace of mind, though I’ve rarely needed to use it.
The upper receiver’s strength lies in its simplicity and adherence to mil-spec standards. Some might find the lack of enhanced features a weakness, such as an ambidextrous design or more aggressive styling. However, its focus on essential functionality is a strength in my view. It meets and exceeds expectations for a standard mil-spec upper receiver.
Design & Ergonomics
The design is typical of an AR-15 upper receiver, with clean lines and a functional aesthetic. The 7075-T6 aluminum construction contributes to a lightweight feel without sacrificing durability. I find it comfortable to handle and manipulate.
There is no learning curve associated with this product. Anyone familiar with the AR-15 platform will find it instantly familiar. The controls are easy to access and operate.
Durability & Maintenance
Given the 7075-T6 aluminum construction and Cerakote finish, this upper receiver is expected to last a long time. With proper care and maintenance, it should withstand years of use. Cleaning is simple and straightforward, using readily available solvents and lubricants.
Repairing the upper receiver is also relatively easy. Should any parts need replacing, they are readily available and can be installed with basic tools. This promotes longevity and usability.
Accessories and Customization Options
The CMMG Mk4/AR15 Upper Receiver Assembly w/Forward Assist does not come with any accessories, as it is a bare upper receiver. However, it is compatible with a vast array of AR-15 accessories. This includes optics, handguards, charging handles, and dust covers.
It readily accepts various barrel lengths and profiles. This further enhances its customization potential. The mil-spec dimensions ensure compatibility with accessories from various manufacturers. Users can easily configure this upper receiver to suit their specific needs and preferences.
Pros and Cons of CMMG Mk4/AR15 Upper Receiver Assembly w/Forward Assist
Pros
- Durable 7075-T6 aluminum construction.
- Mil-spec dimensions ensure compatibility with a wide range of AR-15 parts.
- Smooth and reliable operation with properly functioning BCG and barrel.
- Available in multiple Cerakote finishes for corrosion resistance and customization.
- Affordable price point compared to other high-quality upper receivers.
Cons
- Lacks enhanced features found on more expensive upper receivers (e.g., ambidextrous controls).
- Cerakote finish, while durable, can still be scratched with hard use.
Who Should Buy CMMG Mk4/AR15 Upper Receiver Assembly w/Forward Assist?
This upper receiver is perfect for anyone building an AR-15 from scratch or upgrading an existing rifle. It is well-suited for recreational shooters, home defense enthusiasts, and those seeking a reliable, no-frills upper receiver for general use. The CMMG Mk4/AR15 Upper Receiver Assembly w/Forward Assist balances price and performance.
Those seeking advanced features, such as an ambidextrous design or integral Picatinny rails, should consider a more expensive option. This unit focuses on the essentials. A must-have accessory for this upper receiver is a quality bolt carrier group (BCG) and charging handle.
Conclusion on CMMG Mk4/AR15 Upper Receiver Assembly w/Forward Assist
The CMMG Mk4/AR15 Upper Receiver Assembly w/Forward Assist is a solid and reliable choice for anyone building or upgrading an AR-15. It offers excellent value for the price. The construction is durable, the finish is well-applied, and the overall performance is commendable.
The price is justified for the quality and reputation of CMMG. I would personally recommend this upper receiver to anyone seeking a reliable and affordable foundation for their AR-15 build. If you are building a reliable AR on a budget, then seriously consider buying this CMMG upper!