Davidson Defense Justifier 18-inch Mid-Gas 1:24 .450 Bushmaster AR-15 M-Lok Rifle Full Build Kit

Justifier 18-Inch Mid-Gas 1-24 .450 Bushmaster AR-15 Rifle Full Build Kit

This is an AR-15 full build kit chambered in .450 Bushmaster, centered on a Sepal 18-inch heavy barrel profile 4150 CMV steel barrel with a phosphate finish, a 1-24 twist rate, and a mid-length gas system. The Panhead billet aluminum upper receiver with a black anodized finish and a .458 ejection port door assembly anchors the front end. The mid-length stainless steel gas tube and micro low-profile steel gas block at .750 complete the gas system, and the 15-inch freefloat quad rail handguard covers the forend. A KAK .458 compensator at 5-8x32 closes out the muzzle end. A .458 SOCOM and .450 Bushmaster bolt carrier group and a Mil-Spec M4 charging handle complete the upper side. The lower completion package covers a complete Mil-Spec AR-15 lower parts kit, a Mil-Spec heavy-duty 6-position carbine buffer tube, a standard AR-15 carbine buffer at 3 oz., a standard AR-15 carbine recoil spring made in the USA, a Mil-Spec AR-15 and M16 receiver end plate, and a Mil-Spec AR-15 carbine castle nut. A Davidson Defense AR-15 Ranger stock in black with an A-frame profile and integrated QD sling mounts closes out the rear end. Lower receiver not included.

Key Features

• .450 Bushmaster chambering, Sepal 18-inch heavy barrel profile 4150 CMV steel barrel, phosphate finish
• 1-24 twist rate, 5-8x32 thread pitch
• Mid-length gas system with mid-length stainless steel gas tube
• Micro low-profile steel gas block, .750
• Panhead billet aluminum upper receiver, black anodized, .458 ejection port door assembly
• 15-inch freefloat quad rail handguard
• .458 SOCOM and .450 Bushmaster bolt carrier group
• Mil-Spec AR-15 M4 charging handle
• KAK .458 compensator, 5-8x32 thread pitch
• Black 5-8-inch crush washer
• Complete Mil-Spec AR-15 lower parts kit
• Mil-Spec heavy-duty 6-position carbine buffer tube
• Standard AR-15 carbine buffer, 3 oz.
• Standard AR-15 carbine recoil spring, made in the USA
• Mil-Spec AR-15 and M16 receiver end plate
• Mil-Spec AR-15 carbine castle nut
• AR-15 Ranger stock, black, A-frame profile, adjustable, integrated QD sling mounts, Mil-Spec carbine buffer tube compatible

Perfect For

• AR-15 rifle builders who need everything above the lower receiver for a .450 Bushmaster build
• Shooters pairing this kit with an existing stripped or complete AR-15 lower receiver
• Builders who want a complete .450 Bushmaster component set with a Sepal HBAR barrel, platform-correct BCG, 15-inch freefloat quad rail, and Ranger stock covered in one kit

Upper Assembly

The Panhead billet aluminum upper receiver with a black anodized finish anchors the front end with a .458 ejection port door assembly sized appropriately for the .450 Bushmaster platform. The Sepal 18-inch heavy barrel profile 4150 CMV steel barrel brings a phosphate finish and a 1-24 twist rate to the .450 Bushmaster chamber, threaded at 5-8x32. The mid-length stainless steel gas tube and micro low-profile steel gas block at .750 run a mid-length gas system along the 18-inch barrel. The 15-inch freefloat quad rail handguard surrounds the barrel and gas system along the forend with four full-length Picatinny rail sections running along the top, bottom, and both sides of the handguard body for optics and accessory mounting across all four rail positions.

Bolt Carrier Group and Charging Handle

The .458 SOCOM and .450 Bushmaster bolt carrier group is the platform-correct BCG for this upper, designed around the larger bore diameter of the .450 Bushmaster chambering rather than the standard 5.56 and .223 bolt pattern. The Mil-Spec M4 charging handle pairs with the BCG inside the upper receiver to complete the upper interior and finish the front end of the build.

Muzzle Device

The KAK .458 compensator threads onto the 5-8x32 muzzle end of the barrel. The included black 5-8-inch crush washer seats at the barrel shoulder and completes the muzzle hardware for this kit.

Lower Completion Components

The complete Mil-Spec AR-15 lower parts kit covers the full internal lower component group, including the fire control group, magazine catch, bolt catch, and all associated pins and springs. The Mil-Spec heavy-duty 6-position carbine buffer tube, standard AR-15 carbine buffer at 3 oz., and standard AR-15 carbine recoil spring made in the USA form the buffer system at the rear of the lower. The Mil-Spec AR-15 and M16 receiver end plate and Mil-Spec AR-15 carbine castle nut lock the buffer tube down cleanly at the rear of the lower receiver. The AR-15 Ranger stock in black closes out the rear end with an A-frame adjustable profile and integrated QD sling mounts built directly into the stock body for quick-detach sling attachment on both sides without additional hardware.

Follow safe handling and manufacturer instructions. Ensure compliance with all applicable federal, state, and local laws. Lower receiver not included.