AR57 ULT 12in Barrel 5.7x28mm Upper Receiver Assembly Review

First Impressions of AR57 ULT 12in Barrel 5.7x28mm Upper Receiver Assembly

The AR57 ULT 12in Barrel 5.7x28mm Upper Receiver Assembly is a unique offering in the AR platform world, chambered in the high-velocity, low-recoil 5.7x28mm cartridge. What immediately caught my eye was its unique top-loading magazine design and the promise of reduced over-penetration compared to the ubiquitous 5.56 NATO, making it intriguing for home defense scenarios. It’s an unusual setup that deviates significantly from the standard AR-15, sparking my curiosity as a long-time firearms enthusiast.

I was looking for a compact, controllable AR-platform firearm with sufficient capacity for home defense. The 5.7x28mm round, with its reputation for flat trajectory and manageable recoil, seemed ideal. The top-mounted P90 magazine configuration promised a high round count in a relatively compact package.

Upon unboxing, I was immediately impressed by the overall fit and finish. The AR57 ULT 12in Barrel felt solid and well-constructed, with a smooth, even Melonite finish on the barrel and a clean, anodized finish on the aluminum receiver. The weight felt balanced, not overly heavy for its size, suggesting a well-thought-out design.

Compared to other AR uppers I’ve handled, the AR57 stands out due to its top-loading design. Standard AR uppers, obviously, use a magazine well in the lower receiver. I picked this specifically for its unique features and the 5.7x28mm chambering.

My first impression was a mix of excitement and cautious optimism. The AR57 ULT certainly looked the part, but the proof would be in its performance. It seemed well made but it remains to be seen if the unique design is reliable in practice.

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Real-World Testing: Putting AR57 ULT 12in Barrel 5.7x28mm Upper Receiver Assembly to the Test

First Use Experience

I tested the AR57 ULT at my local outdoor shooting range. The weather was clear and relatively cool, around 60 degrees Fahrenheit, with a slight breeze.

The AR57 performed reliably through the first 100 rounds, using both FN and Federal American Eagle ammunition. The recoil was incredibly mild, even more so than I anticipated, making it easy to stay on target for rapid follow-up shots. There were no immediate issues, but the top-loading magazine required some familiarization.

Extended Use & Reliability

After several range sessions spanning several months, the AR57 ULT has proven to be fairly reliable. I’ve put roughly 500 rounds through it with only a couple of minor hiccups, both occurring with a specific aftermarket magazine.

Durability has been excellent; there are no noticeable signs of wear and tear beyond the expected scuff marks on the brass deflector. Cleaning is relatively straightforward, requiring only standard AR-15 cleaning procedures. The AR57 has lived up to expectations, providing a unique and enjoyable shooting experience.

Breaking Down the Features of AR57 ULT 12in Barrel 5.7x28mm Upper Receiver Assembly

Specifications

• Caliber: 5.7x28mm. This offers a high-velocity, flat-shooting round with low recoil.
• Overall Length: 24.5 inches. This compact size makes it maneuverable in tight spaces.
• Barrel Length: 12 inches. The shorter barrel contributes to the overall compactness.
• Barrel Twist Rate: 1-8.5. This twist rate is optimized for stabilizing the 5.7x28mm bullet.
• Threads per Inch: 1/2×28. This allows for the attachment of common muzzle devices.
• Muzzle Device: Muzzle Brake. This helps to further reduce felt recoil and muzzle rise.
• Finish: Melonite. This provides excellent corrosion resistance and durability.
• Material: 8620 Alloy Steel (barrel), 7075-T6 Aircraft Grade Aluminum (receiver). These materials ensure strength and longevity.
• Rifling Profile: 6 Groove Rifling. This contributes to accuracy and bullet stabilization.
• Mount Type: Picatinny. This allows for easy attachment of optics and accessories.

These specifications are crucial because they define the AR57‘s performance characteristics. The 5.7x28mm caliber provides a unique combination of power and controllability. The quality materials and construction suggest a long service life.

Performance & Functionality

The AR57 ULT performs exceptionally well in its intended role as a compact, high-capacity firearm. Accuracy is surprisingly good for a 12-inch barrel, easily achieving tight groupings at 50 yards.

Its strengths lie in its low recoil, high capacity, and compact size. A potential weakness is the unfamiliar top-loading magazine, which might require some training to master. It meets my expectations for a fun, unique, and effective AR-platform firearm.

Design & Ergonomics

The AR57 boasts a well-thought-out design, with the top-loading magazine being its defining feature. The build quality is excellent.

The weight is balanced, and the ergonomics are generally good, though the magazine placement takes some getting used to. There is a slight learning curve to using a top-loading magazine system.

Durability & Maintenance

Based on my experience, the AR57 ULT appears to be built to last. The Melonite finish and high-quality materials should provide years of reliable service.

Maintenance is straightforward, requiring only standard AR-15 cleaning procedures. The design is simple and robust, minimizing potential points of failure.

Accessories and Customization Options

The AR57 ULT comes standard with a muzzle brake. The Picatinny rail on top allows for easy mounting of optics, such as red dots or scopes.

It is compatible with most AR-15 lower receivers and triggers. There are various aftermarket magazines available, although I recommend sticking with reputable brands for optimal reliability.

Pros and Cons of AR57 ULT 12in Barrel 5.7x28mm Upper Receiver Assembly