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Achieve the ultimate balance of compact maneuverability and reliable rifle-length performance with the PRO2A 13.7" 5.56 NATO Mid Length Melonite M-LOK Upper Kit. This 100% American-made master build bundle contains every critical component required to transform a standard stripped lower receiver into a highly mobile tactical asset. Built around a premium 13.7-inch 4150 CMV steel barrel, this kit features a versatile 1:7 twist rate engineered to stabilize a wide range of heavier projectile weights with exceptional consistency. Complete with a pre-headspaced M16 bolt carrier group, standard charging handle, complete lower parts kit (LPK), and a matching 6-position carbine buffer stock assembly, this all-inclusive package takes the guesswork out of building your next compact weapon system.
| Upper Receiver Assembly | Mil-Spec Forged 7075-T6 Aluminum, M4 Feed Ramps, Forward Assist & Port Cover, Type III Hardcoat Anodized Black Finish |
|---|---|
| Bolt Carrier Group | Full M16 Profile, Heavy-Duty 9310 Steel Bolt Face, Nitride Finish, Heavy Duty Carrier, Properly Staked Gas Key & MPI Tested |
| Charging Handle | Standard Mil-Spec Aluminum Charging Handle Assembly |
| Barrel Component | 13.7 Inch Profile, 4150 Chrome Moly Vanadium (CMV) Steel, Medium Contour, Melonite Treated Interior & Exterior Bore |
| Caliber | 5.56 NATO (Accepts .223 Remington) |
| Twist Rate | 1:7 Twist |
| Gas Operating Block & System | Mid-Length Gas System, Low-Profile Gas Block Machined from 4140 Steel, Stainless Steel Gas Tube |
| Muzzle Device Component | Standard 1/2x28 Thread Pitch, A2 Birdcage Flash Hider with Crush Washer Pre-Installed |
| Handguard Rail | 12 Inch Slim Profile Free-Float Aluminum Handguard, Continuous Top Picatinny Alignment, Modular M-LOK Attachment Points |
| Lower Receiver Parts Kit (LPK) | Complete Mil-Spec Spring and Pin Kit, Polished Single-Stage Hammer and Trigger Assembly, Standard A2 Pistol Grip |
| Brace | Adjustable Blade, Pistol Buffer Tube, Standard 3oz Carbine Buffer, and High-Tensile Buffer Spring |
| Manufacturing Origin | 100% Assembled and Quality Checked in the USA with Pro2A Tactical Lifetime Factory Warranty |
Piecing together a precision rifle build from separate sources often introduces compounding tolerances, leading to headspacing headaches, short-cycling issues, or poor accuracy. The PRO2A 13.7" 5.56 NATO Upper Kit directly bypasses these frustrations. Every component in this master package—from the hand-assembled free-float upper to the lower receiver internal springs, buffer weight, and bolt carrier group—is pre-selected and optimized to interface perfectly out of the box. Offering a highly sought-after 13.7-inch barrel length that optimizes hand-held agility with a mid-length gas system, this complete build bundle is the ultimate way to achieve premium, reliable performance without paying individual part premiums.
| SKU | P2A556AX12MID137-BA-KIT |
|---|---|
| Barrel Length | 13.7 inch |
| Rifle Caliber | 5.56 NATO |
| Manufacturer | Pro2A Tactical |
