PRO2A 8.5" 40 S&W 1/16 Pistol Caliber Melonite M-LOK AR-15 Upper Receiver

Bring hard-hitting, reliable pistol caliber performance to your AR platform with this premium 100% American-made upper receiver assembly. The PRO2A 8.5" 40 S&W Pistol Caliber Upper anchors a match-ready, premium Melonite-treated 4150 CMV barrel to a mil-spec forged upper receiver optimized for blowback operation. Complete with a specialized 40 S&W Nitride bolt carrier group, an ultra-slim free-float M-LOK handguard, and a pre-installed standard muzzle device, this assembly delivers everything required to seamlessly convert your dedicated pistol caliber lower or mag-well adapted configuration into a fast-handling, flat-shooting tactical asset.

Key Features

Specialized 40 S&W Nitride Bolt Carrier Group: Engineered precisely out of premium 8620 steel with a slick nitride finish. Featuring a duty-ready M16 profile and magnetic particle testing (MPI), it ensures uniform case extraction and rock-solid reliability across commercial and defense ammunition profiles.
Heavy-Duty Melonite Barrel Protection: The 8.5-inch 4150 CMV steel barrel is fully treated with an advanced Salt Bath Melonite finish inside and out. This premium chemical hardening vastly extends bore life against rapid gas erosion at the port and shields against moisture.
Precision 1:16 Right-Hand Twist: Precision button-rifled with a 1:16 twist configuration explicitly tailored to stabilize standard and heavy-grain 40 S&W projectiles, delivering tight grouping profiles and uniform downrange velocity.
Optimum 8.5-Inch Maneuverability: Strikes the perfect length balance between close-quarters mobility and barrel length velocity metrics, providing a highly responsive weapon blueprint for personal defense or competitive PCC configurations.
Slim Profile Free-Float M-LOK Rail: Crafted from premium 6061-T6 aluminum, the free-float rail isolates barrel vibrations to preserve uniform mechanical accuracy while providing massive M-LOK modular real estate.

Technical Specifications

Upper Receiver	Pistol Caliber Specific Slick-Side Upper Receiver, Forged 7075-T6 Aluminum, Optimized Ejection Port, Type III Hardcoat Anodized Black
Barrel Length & Steel	8.5 Inch Profile, 4150 Chrome Moly Vanadium Steel, Medium Contour, Melonite Treated
Caliber	40 S&W
Twist Rate	1:16 Twist (Optimized to stabilize standard and heavy intermediate pistol caliber projectile profiles)
Operating System	Direct Blowback System (No gas block required for maximum mechanical simplification and feeding reliability)
Muzzle Device	9/16-24 Thread Pitch, A2 Birdcage Flash Hider with Crush Washer Pre-Installed
Handguard	7 Inch Slim Profile Free-Float M-LOK Rail, Full-Length Top Picatinny Rail, Machined from 6061-T6 Aluminum
Manufacturing Origin	100% Made in the USA with Pro2A Tactical Lifetime Factory Warranty

Why Choose This Product?

The PRO2A 8.5" 40 S&W Pistol Caliber Melonite M-LOK Upper directly solves the three biggest hurdles facing pistol caliber carbine builders: mechanical over-complication, component-to-cartridge mismatching, and unpredictable feed timing. While traditional rifle-caliber platforms rely on complex gas block mechanics that require constant tracking and dwell tuning, this dedicated system runs on a reliable, simplified blowback system paired with a pre-headspaced, caliber-matched Nitride bolt carrier group. This configuration ensures smooth casing extraction and rapid cycling out of the box with standard PCC lowers and mag configurations.

Opting for an 8.5-inch medium contour barrel path offers a massive physical advantage for defensive operators and recreational shooters alike. It delivers a compact, nimble footprint that maneuvers around close-quarters barriers effortlessly while allowing the hard-hitting 40 S&W cartridge enough bore space to realize full velocity potential and clean powder burning. Furthermore, by investing in a master-built conversion upper rather than piecing your components together block-by-block, you eliminate dangerous out-of-spec feeding issues. Backed completely by Pro2A Tactical's signature Lifetime Factory Warranty and engineered with 100% American craftsmanship, this premium upper converts your lower receiver into a fast-handling, duty-ready asset with absolute confidence.