PRO2A 18" 450 Bushmaster 1/24 Mid Length Melonite NR Side Charging M-LOK AR-15 Upper Kit

Product Overview

The PRO2A 18" 450 Bushmaster 1/24 Mid Length Melonite NR Side Charging M-LOK AR-15 Upper Kit delivers hard-hitting straight-walled ballistic performance optimized for long-range hunting and tactical deployments. Completely chambered in .450 Bushmaster, this comprehensive master builder package removes the standard rear latch layout, replacing it with a premium Left-Side Non-Reciprocating (NR) Charging Upper Receiver system. Built with a premium 18-inch 4150 CMV heavy-profile barrel to squeeze maximize velocity from the cartridge, the system arrives completely assembled, headspaced, and timed on the upper receiver. This master package ships bundled with a caliber-matched side-charging profile Nitride bolt carrier group, a full lower parts kit, and a 6-position adjustable carbine buttstock setup to finish your build right out of the box.

Key Features

Non-Reciprocating Side Charging (NRSC) Handle: Streamlines ergonomic operation by keeping the left-side charging handle stationed forward while firing—preventing moving interference with support rests while enabling instant cycling without breaking your cheek weld.
Complete Master Build Configuration: Speeds up project logistics by completely grouping a pre-assembled side-charge upper receiver, pre-headspaced side-charging bolt group, complete internal lower parts kit hardware, and a matching stock buffer tube completion bundle.
Modified Big-Bore Upper Receiver: Built with an enlarged, precision-relieved ejection port track specifically engineered to facilitate flawless, high-velocity extraction clearance for massive .450 straight-wall brass.
Optimized Mid-Length Gas Impingement: Perfectly matches cyclic gas dwell times to the 18-inch barrel profile through a 0.750" low-profile gas block, smoothing out the aggressive impulse curve of the large straight-wall round.
Inside-Out QPQ Melonite Protection: High-performance liquid salt-bath nitride surface treatment safeguards uniform land-and-groove rifling against intense gas erosion while providing total immunity to wet environmental corrosion.
Slim Free-Float M-LOK Handguard: Isolates structural barrel harmonic variables to shield uniform downrange grouping accuracy while establishing continuous top Picatinny rail space and modular side mounting real estate.

Technical Specifications

Charging System Style	Left-Side Non-Reciprocating (NR) Side-Charging Upper Assembly; Forward Handle Remains Stationary While Firing
Upper Receiver	Gibbz Arms G4 Billet Aluminum, Custom-Enlarged Ejection Port for Big-Bore Brass Clearance, Type III Hardcoat Anodized Matte Black Finish
Bolt Carrier Group (BCG)	Milspec M16 Profile, Heavy-Duty M16 Carrier, 9310 Steel Bolt, Slick QPQ Black Nitride Treatment, MPI Inspected, Properly Configured Staked Gas Key Layout
Barrel Length & Contour	18 Inches; Heavy Contour Profile Axis
Barrel Material Composition	4150 Chrome Moly Vanadium (CMV) Structural Steel
Twist Rate Optimization	1:24 Twist (Precision-engineered to stabilize heavy .450 straight-wall projectiles flawlessly)
Barrel Lining Coating	QPQ Melonite / Liquid Salt Bath Nitride Interior Bore and Exterior Finish for Maximum Erosion Resistance
Gas Operating Loop	Mid-Length Gas System with 0.750" Low Profile Gas Block, High-Tensile Stainless Steel Gas Tube
Muzzle Thread Pitch & Device	5/8x24 TPI (Thread Pitch Layout); Equipped with Standard A2 Big-Bore Flash Hider Combination
Handguard Rails Profile	15 Inch Slim Profile Free-Float Aluminum Handguard, Integrated Top Picatinny Rail Alignment, Matrixed M-LOK Structural Slots
Lower Receiver Parts Kit (LPK)	Complete Mil-Spec Internal Hardware Small Components (Springs, Detents, Pins), Single-Stage Fire Control Trigger Group Assembly (Trigger, Hammer, Disconnector), and Standard Mil-Spec A2 Pistol Grip
Buttstock Assembly Setup	6-Position Adjustable M4 Buttstock, Mil-Spec Diameter Receiver Extension Tube, 3oz Carbine Buffer, and High-Tensile Recoil Buffer Spring Group
Manufacturing Origin & Quality	100% Proudly Assembled, Timed, and Quality Checked in the USA with Pro2A Tactical Lifetime Factory Warranty

Why Choose the PRO2A Non-Reciprocating Side-Charging 450 Bushmaster Rifle Kit?

Harnessing a thumping .450 straight-walled cartridge inside an AR-15 platform demands precision engineering from the bolt lugs to the receiver frame. Standard rifle receivers cause catastrophic stovepipe malfunctions and failure-to-extract errors because narrow mil-spec ejection openings cannot clear wide straight-walled brass. Pro2A Tactical eliminates this engineering barrier directly on the manufacturing line—utilizing custom-expanded ejection channel tracks paired with a matching, pre-headspaced side-charging 9310 steel bolt face to guarantee consistent extraction strings. By moving the cycle layout to a left-side ergonomic handle, you can clear chamber actions or load heavy rounds intuitively while keeping your eyes completely downrange, overcoming the awkward clearance issues of large hunting optics and standard charging latches. By aligning an ultra-hard 18" Melonite heavy barrel to an integrated mid-length gas loop, a full internal lower hardware group, and an adjustable carbine buttstock, this master build kit delivers a cycle-tuned, unified shooting ecosystem designed for absolute straight-wall reliability.