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

Product Overview

The Pro2A Left Hand 13.7" 5.56 NATO Mid Length Upper Receiver offers the perfect solution for southpaw shooters 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 left-ejecting 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, minimized component wear, and clears gas blowback away from left-handed operators.

Key Features

True Left-Hand Mirroring: Dedicated left-handed upper layout features a left-side ejection path to route hot brass, debris, and gas entirely away from the shooter's line of sight.
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.

Technical Specifications

Upper Receiver	Milspec Dedicated Left-Hand Ejection Pattern, Billet Aluminum, Hardcoat Anodized Black, M4 Feed Ramps
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?

Left-Handed Tactical Carbine Operators

Southpaw 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 keeping spent casings out of their face.

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.

Left-Handed AR-15 Builders Demanding Drop-In Modularity

Custom gunsmiths aiming to update a standard small-frame lower into a mirrored, lightweight utility weapon choose this complete upper. It snaps easily onto standard mil-spec lower assemblies using a left-handed BCG, bypassing home assembly risks.