Stern Defense SD 4in MOD4 MLOK .40SW Upper Receiver Assembly Review

First Impressions of Stern Defense SD 4in MOD4 MLOK .40SW Upper Receiver Assembly

The Stern Defense SD 4in MOD4 MLOK .40SW Upper Receiver Assembly promises a compact, powerful, and versatile platform for the AR-15 enthusiast looking to venture into the .40 S&W realm. Stern Defense aims to deliver a high-quality upper receiver group that seamlessly integrates with Glock magazines and offers a unique shooting experience. This assembly immediately piqued my interest due to its potential for use in close-quarters scenarios and its compatibility with readily available Glock magazines.

As someone with over a decade immersed in the world of tactical gear, I’m constantly searching for innovative solutions that offer a tangible advantage. My quest for a compact, reliable, and easily configurable CQB platform led me to the Stern Defense upper. The allure of a .40 S&W AR pistol that utilizes ubiquitous Glock magazines was too strong to resist.

Upon unboxing, the first thing that struck me was the robust feel of the components. The 7075-T6 aluminum receiver felt incredibly solid, and the M-LOK handguard provided a comfortable and secure grip. The fit and finish were impressive, indicating a commitment to quality craftsmanship.

Compared to similar pistol caliber AR upper receivers I’ve handled from CMMG and Angstadt Arms, the Stern Defense offering seemed to strike a balance between compact size and robust construction. I chose the Stern Defense because of its dedicated .40 S&W design and promise of seamless Glock magazine integration. My initial impression was one of cautious optimism – excited about the possibilities, but eager to put it through its paces.

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Real-World Testing: Putting Stern Defense SD 4in MOD4 MLOK .40SW Upper Receiver Assembly to the Test

First Use Experience

My first range trip with the Stern Defense SD 4in MOD4 MLOK .40SW Upper Receiver Assembly was at an outdoor range with varying distances. The primary objective was to test reliability and accuracy with different loads of .40 S&W ammunition. I experienced a wide range of weather conditions, from bright sunshine to a brief but heavy rain shower.

In dry conditions, the upper performed admirably, cycling flawlessly with both 165-grain and 180-grain FMJ rounds. However, the initial magazines I was using had slight feed issues. I did have a few failures to feed when things got a bit wet due to water getting into the ejection port, resulting in a slightly gritty action.

After a few magazines, I did find myself getting accustomed to the recoil impulse of the .40 S&W cartridge in such a short-barreled platform. There was a slight learning curve, but nothing too dramatic.

Extended Use & Reliability

After several weeks of consistent use, the Stern Defense upper has proven to be impressively reliable. Minor initial magazine related issues aside, there were no functional concerns. Regular cleaning and lubrication are necessary to keep it running smoothly, as is to be expected.

The hard-coat anodized finish has held up well, showing only minor signs of wear around the ejection port and charging handle. Cleaning is relatively straightforward, requiring only basic AR-15 cleaning tools and solvents. This upper receiver assembly is a step up from previous builds I’ve worked with due to its rock-solid performance.

Breaking Down the Features of Stern Defense SD 4in MOD4 MLOK .40SW Upper Receiver Assembly

Specifications

The Stern Defense SD 4in MOD4 MLOK .40SW Upper Receiver Assembly boasts several noteworthy specifications. It is chambered in .40 S&W and features a 4-inch barrel with a 1-16 twist rate. These specs make it ideal for close-quarters engagements where maneuverability and stopping power are paramount.

The upper receiver is constructed from 7075-T6 aluminum, while the handguard is made from 6061 aircraft grade aluminum, both hard-coat anodized for durability. The M-LOK compatible handguard offers versatile attachment points for accessories. The overall weight is a mere 15.5 oz, and it comes with a MIL-SPEC bolt carrier group, but no magazine is included.

These specifications are important because they directly impact the upper’s performance, durability, and adaptability. The high-quality materials ensure longevity, while the compact size enhances maneuverability. The M-LOK system allows for easy customization with lights, lasers, and other tactical accessories.

Performance & Functionality

The Stern Defense SD 4in MOD4 MLOK .40SW Upper Receiver Assembly performs admirably, delivering good accuracy and consistent reliability. The 4-inch barrel delivers a significant punch, making it suitable for defense and tactical applications. It is highly reliable with a variety of ammunition, assuming you have a solid magazine.

The primary strength lies in its compact size and powerful cartridge. The weakness is the increase in felt recoil with such a short barrel in .40SW. Overall, it meets expectations as a CQB platform, but there is room for improved recoil management.

Design & Ergonomics

The build quality is excellent, with tight tolerances and a robust feel. The materials used are top-notch, providing a sense of confidence in its durability. The M-LOK handguard provides a comfortable and secure grip.

There is a slight learning curve due to the unique recoil impulse of the .40 S&W cartridge in such a short barrel, but overall, it is relatively user-friendly.

Durability & Maintenance

Given the high-quality materials and construction, the Stern Defense SD 4in MOD4 MLOK .40SW Upper Receiver Assembly is expected to last a long time with proper care. The hard-coat anodized finish provides excellent protection against wear and corrosion. Regular cleaning and lubrication are essential to maintain optimal performance.

Accessories and Customization Options

The Stern Defense SD 4in MOD4 MLOK .40SW Upper Receiver Assembly readily accepts a wide range of AR-15 accessories. The M-LOK handguard allows for the attachment of lights, lasers, vertical grips, and other tactical accessories. It is compatible with any standard AR-15 lower receiver and accepts Glock magazines via a dedicated magazine adapter (sold separately).

Popular accessories include red dot sights, weapon lights, and slings. Compatibility with other brands is excellent, thanks to the use of standard AR-15 interfaces. A quality brace or stock is highly recommended to enhance stability and control.

Pros and Cons of Stern Defense SD 4in MOD4 MLOK .40SW Upper Receiver Assembly