The One Horse OH 10.5 300BLK Complete Upper Receiver brings together a 10.5-inch .300 AAC Blackout barrel, free-float M-LOK handguard, and included bolt carrier group for a ready-to-pin AR-15 upper. Built around a medium-profile, pistol-length gas barrel with 1:7 twist and 5/8x24 threaded muzzle with flash hider, it is designed to run both subsonic and supersonic loads with dependable performance.

This upper is well suited for compact AR pistols or registered SBR builds where maneuverability and balance matter, and it pairs with any standard mil-spec AR-15 lower. The slim M-LOK handguard offers ample space for lights or other accessories while keeping weight in check, and the nitride-finished BCG and charging handle arrive installed so you can get to the range with minimal setup. One Horse’s attention to materials, including a 4150 steel barrel and mil-spec construction, reflects a focus on durability and consistent craftsmanship.

Key Features:

• Manufacturer: One Horse
• Model: OH 10.5 300BLK Complete Upper Receiver (OH-CU05)
• Caliber: .300 AAC Blackout
• Barrel Length: 10.5 in
• Barrel Twist Rate: 1:7
• Firearms Threads Per Inch: 5/8x24
• Gas System Length: Pistol Length
• Handguard: 10 in M-LOK free-float
• Included Components: Complete upper, nitride BCG, charging handle
• Compatibility: Mil-spec AR-15 lowers