Details
Tunnel Scout 18-Inch Mid-Length-Gas 1-24 .450 Bushmaster AR-15 Freefloat Tubular M-LOK Handguard Rifle Complete Upper
This is a complete AR-15 upper chambered in .450 Bushmaster, built around an 18-inch HBAR 4150 CMV steel barrel with a phosphate finish and a 1-24 twist rate specific to the .450 Bushmaster chambering. The Panhead billet upper receiver with a widened .458 ejection port cut anchors the front end with a profile purpose-built for the larger bore diameter of this chambering. The 15-inch tubular M-LOK aluminum handguard brings a suppressor ready design with a 1.77-inch internal diameter that accommodates suppressor use along the forend. A .458 SOCOM and .450 Bushmaster compatible bolt carrier group and an M4 Mil-Spec charging handle complete the upper component set.
Key Features
- .450 Bushmaster chambering, 18-inch HBAR 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 inch
- Panhead billet upper receiver, .458 ejection port door cut
- AR-15 ejection port door assembly
- 15-inch tubular M-LOK aluminum handguard, suppressor ready, 1.77-inch internal diameter
- .458 SOCOM and .450 Bushmaster compatible bolt carrier group
- AR-15 M4 Mil-Spec charging handle
- KAK .458 compensator, 5-8x32 thread pitch
- Black 5-8-inch crush washer
Perfect For
- AR-15 builders pairing a complete .450 Bushmaster upper with an existing lower
- Shooters adding an 18-inch .450 Bushmaster upper to an AR-15 lower they already own
- Builders who want a BCG and charging handle included with a purpose-built .450 Bushmaster upper assembly
Upper Receiver and Barrel
The Panhead billet upper receiver sets the tone for this front end with its widened .458 ejection port cut, a purpose-built feature for the larger case diameter of the .450 Bushmaster chambering that a standard AR-15 ejection port does not accommodate as cleanly. An AR-15 ejection port door assembly is included as part of the upper. The 18-inch HBAR 4150 CMV steel barrel brings a phosphate finish and a 1-24 twist rate to the .450 Bushmaster chamber, threaded at 5-8x32, a thread pitch specific to this bore diameter. The mid-length stainless steel gas tube and micro low-profile steel gas block at .750 inch run a mid-length gas system along the barrel, a well-matched gas system length for an 18-inch barrel profile on this platform.
Tubular M-LOK Handguard
The 15-inch tubular M-LOK aluminum handguard surrounds the barrel and gas system along the freefloat forend with a suppressor ready design built around a 1.77-inch internal diameter. That internal diameter gives the builder clearance to run a suppressor under the handguard without interference. M-LOK slots run along the handguard body for accessory attachment across the forend. The tubular profile keeps the overall front end clean and consistent from the upper receiver to the muzzle end.
Bolt Carrier Group and Charging Handle
The included bolt carrier group is compatible with both .458 SOCOM and .450 Bushmaster, making it the correct BCG choice for this chambering on the AR-15 platform. Standard AR-15 bolt carrier groups are not compatible with the .450 Bushmaster bore diameter, and this BCG addresses that platform-specific requirement directly. The M4 Mil-Spec charging handle pairs with the BCG inside the upper receiver to complete the upper interior. These two components finish the upper side and give the kit a fully matched front end specific to the .450 Bushmaster chambering.
Muzzle Device
The KAK .458 compensator threads onto the 5-8x32 muzzle end of the barrel, a thread pitch and caliber designation specific to the .450 Bushmaster bore diameter. The included black 5-8-inch crush washer seats at the barrel shoulder and completes the muzzle hardware for this upper. The KAK .458 compensator is a purpose-built muzzle device for this chambering and thread pitch combination.
Follow safe handling and manufacturer instructions. Ensure compliance with all applicable federal, state, and local laws.
