Pro2A 5.5" 40 S&W Pistol Caliber Melonite M-LOK AR-40 Upper Receiver

PRO2A 5.5" 40 S&W 1/16 Pistol Caliber Melonite M-LOK Upper

Description

The Pro2A Tactical 5.5-inch .40 S&W Pistol Caliber Complete Upper Receiver assembly delivers dependable blowback reliability and hard-hitting performance in an ultra-compact footprint. Carefully hand-assembled and quality verified in Georgia, this upper receiver operates on a standard, hyper-reliable straight blowback operational system. Featuring a highly maneuverable 5.5-inch barrel with a premium Melonite treatment and a rigid free-float M-LOK rail layout, it serves as an excellent drop-in option for dedicated AR-40 pistol lower configurations or registered short-barreled rifle receivers.

Key Features

Ultra-Compact Maneuverability: Packs a hard-hitting .40 S&W caliber punch into a tight 5.5-inch barrel profile ideal for close-quarters training, vehicle storage, and low-recoil home defense layouts.
Reliable Straight Blowback Action: Built without gas blocks or complex gas tube routing, eliminating standard mechanical failure points to ensure dependable cycling with a wide variety of factory ammunition.
1/16 Standard Twist: Precision-stabilizes standard 165gr and 180gr flat-nose .40 S&W projectiles comfortably for reliable target groupings.
Slim M-LOK Modular Rail: Employs a lightweight free-float handguard for easy integration of hand stops, tactical flashlights, and M-LOK accessories.

Technical Specifications

Upper Receiver	Milspec Billet Aluminum M4 Flat Top Receiver, Ejection Port Optimized for Pistol Calibers, Enhanced Feed Cone (Type III Hardcoat Anodized)
Barrel Length & Profile	5.5-Inch Medium Profile
Caliber	.40 S&W (Smith & Wesson)
Twist Rate	1:16 Twist
Barrel Material	4150 Chrome Moly Vanadium Steel with Premium Corrosion-Resistant Melonite Finish
Gas System Length	Not Needed - Straight Blowback Operation
Handguard	4 Inch Free Float Slim Profile M-LOK Rail System with Integrated Top Picatinny Rail
Muzzle Thread & Device	9/16x24 Thread Pitch with Standard A2 Flash Hider

Why Choose This Product?

Transitioning into a dedicated pistol caliber carbine or heavy pistol configuration requires precise chamber geometry and extraction compliance due to the straight blowback cycling pressures. The Pro2A 5.5" .40 S&W Upper Receiver addresses this challenge entirely by utilizing an optimized feed ramp contour matched alongside premium 4150 steel manufacturing tolerances. The resilient Melonite surface treatment guarantees maximum bore life, exceptional surface hardness, and worry-free cleanings after using dirty training ammunition. Safe, ultra-flat shooting, and built to withstand rigorous use, it is the perfect drop-in conversion to round out any versatile AR layout.

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