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

Justifier 18-Inch Mid-Gas 1-24 .450 Bushmaster AR-15 Rifle Complete Upper

This is a complete AR-15 upper chambered in .450 Bushmaster, built around 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 component set.

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

Perfect For

• AR-15 rifle builders pairing a complete .450 Bushmaster upper with an existing lower
• Shooters adding an 18-inch .450 Bushmaster upper to a standard AR-15 lower they already own
• Builders who want a platform-correct .458 SOCOM and .450 Bushmaster BCG and charging handle included with a Sepal HBAR barrel and 15-inch freefloat quad rail in one complete upper assembly

Upper Receiver and Barrel

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. These two components complete the upper component set alongside the upper assembly, barrel, and handguard.

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 upper.

Follow safe handling and manufacturer instructions. Ensure compliance with all applicable federal, state, and local laws.