One Horse 16" 300 BLK Complete Upper Receiver

15" M-LOK Handguard - Nitride BCG - Made in USA Upgrade your rifle with this dependable 16" .300 BLK complete upper receiver. Built for accuracy and smooth performance, it features a free-float 15" M-LOK handguard for solid accessory mounting and improved barrel stability. The nitride BCG delivers reliable cycling and low-maintenance durability, while the full-length Picatinny rail provides plenty of room for optics. Ready to pin onto any Mil-Spec lower, this upper is built in the U.S.A. and ready for work. Includes 16" .300 BLK barrel with SOCOM profile and 1:7 twist, 15" M-LOK free-float handguard, nitride BCG, charging handle, A2 flash hider, and clamp-on system with steel barrel nut and screws. 4150 steel barrel, pistol-length gas system, 5/8x24 threading. SKU: OH-CU04.

16" SOCOM Barrel with 1:7 Twist

The 16" barrel features SOCOM profile manufactured from 4150 steel with 1:7 twist rate. The SOCOM profile provides balance between weight and heat dissipation while the 1:7 twist stabilizes both subsonic and supersonic .300 BLK ammunition. Threaded 5/8x24 with A2 flash hider.

15" M-LOK Free-Float Handguard

The 15" M-LOK free-float handguard provides solid accessory mounting capability while improving barrel stability. The free-float design ensures barrel harmonics remain unaffected by handguard pressure or mounted accessories. M-LOK slots enable low-profile attachment without the weight of continuous rails.

Nitride BCG

The nitride bolt carrier group delivers reliable cycling and low-maintenance durability. The nitride coating provides exceptional hardness and corrosion resistance while reducing friction for smooth operation. The coating eliminates the need for chrome-lining while improving wear resistance.

Pistol-Length Gas System

The pistol-length gas system is optimized for 16" .300 BLK barrels. The shorter gas system provides proper dwell time for reliable cycling with both subsonic and supersonic ammunition.

Made in USA

Every One Horse rifle and component is made in America with uncompromising standards. U.S.-sourced materials, U.S. manufacturing, and strict quality control at every step. No shortcuts, no imported surprises—just dependable parts built by people who take pride in American craftsmanship.

Mil-Spec Compatible

Ready to pin onto any Mil-Spec lower receiver. The upper follows standard AR-15 specifications for drop-in compatibility with mil-spec lower receivers. The One Horse 16" 300 BLK complete upper delivers reliable performance with American craftsmanship—modular and ready to run.

SPECIFICATIONS

• Manufacturer: One Horse
• SKU: OH-CU04
• Type: Complete Upper Receiver
• Caliber: .300 BLK (300 Blackout)
• Barrel Length: 16 inches
• Barrel Profile: SOCOM
• Barrel Material: 4150 Steel
• Twist Rate: 1:7 inches
• Gas System: Pistol-Length
• Muzzle Thread: 5/8x24
• Muzzle Device: A2 Flash Hider
• Handguard: 15" M-LOK Free-Float
• Handguard System: Clamp-On with Steel Barrel Nut and Screws
• Top Rail: Full-Length Picatinny
• Bolt Carrier Group: Nitride (included)
• Charging Handle: Included
• Lower Receiver Compatibility: Mil-Spec AR-15
• Country of Origin: U.S.A.
• Manufacturing: American Made (U.S.-sourced materials, U.S. manufacturing)