PRO2A 13.7" 5.56 NATO 1/7 Mid Length Melonite M-LOK AR-15 Upper - Pinned & Welded

Product Overview

The Pro2A 13.7" 5.56 NATO Mid Length Upper Receiver offers the perfect solution for operators searching for the absolute shortest rifle-length footprint without stepping into NFA short-barreled rifle regulations. Chambered in the universally trusted 5.56 NATO (fully backward-compatible with .223 Remington), this premium upper features a muzzle device that is permanently pinned and welded to the barrel threads to legally satisfy the 16-inch federal requirement. Paired with a smooth-cycling mid-length gas operating block, this setup delivers significantly reduced felt recoil and minimized component wear.

Key Features

Permanently Pinned & Welded Muzzle: Structurally brings the overall length of the compact 13.7-inch barrel to a legal 16 inches, avoiding mandatory NFA tax stamps and paperwork.
Smooth Mid-Length Gas Operating System: Drops chamber pressures to achieve a softer recoil impulse and faster follow-up shot tracking compared to standard carbine-length gas layouts.
Versatile 1:7 Twist Rate: Optimized to stabilize heavier defensive, tactical, and match-grade ammunition loads ranging from 62 grains up to 77 grains.
Mil-Spec Modularity: Crafted with a premium free-float M-LOK handguard and forged receiver structure to seamlessly drop right onto any standard AR-15 lower frame.

Technical Specifications

Upper Receiver	Standard AR-15 Format, Forged 7075-T6 Aluminum, Hardcoat Anodized Black, M4 Feed Ramps (Forward Assist & Dust Cover Pre-Installed)
Barrel Length & Profile	13.7-Inch Government Profile (Brings overall barrel length to a legal 16-inches via pinned and welded muzzle device)
Caliber	5.56 NATO (.223 Remington Compatible)
Twist Rate	1:7 Twist
Barrel Material & Treatment	4150 Chrome Moly Vanadium Steel, Premium Corrosion-Resistant Melonite Finish
Gas Operating Block	Mid-Length Direct Impingement, 0.750" Low-Profile Steel Gas Block, Stainless Steel Gas Tube
Muzzle Thread & Device	1/2x28 Thread Pitch, "Pro2A Flash Guardian 3 Prong Flash Hider" Permanently Pinned & Welded to ATF Compliance Standards
Handguard Rail	12" Slim Free-Float M-LOK Handguard, Machined from 6061-T6 Aluminum with Top Picatinny Rail Layout
Manufacturing Origin	100% Made in the USA with Pro2A Tactical Lifetime Factory Warranty

Who Chooses This Upper Receiver?

Tactical Carbine Operators

Shooters wanting the maximum handling advantages of a short-barreled carbine without legal restrictions pick this 13.7-inch build. The permanently attached muzzle assembly preserves a true rifle classification while dramatically cutting front-end weight.

Hard-Use Duty Marksmen

Operators looking for a reliable, soft-shooting platform choose the mid-length gas system configuration. It extends the longevity of standard cycling components, lowers the mechanical strain on internal parts, and keeps muzzle rise highly predictable.

AR-15 Builders Demanding Drop-In Modularity

Custom gunsmiths aiming to update a standard small-frame lower into an innovative, heavy-hitting utility weapon choose this complete upper. It snaps easily onto mil-spec lower assemblies, bypassing home assembly risks.