ONE HORSE 300BLK COMPLETE UPPER RECEIVER W/MEDIUM PISTOL BBL FOR AR-15 Build a compact, hard-hitting AR platform with this .300 Blackout complete upper receiver, designed for reliability, maneuverability, and close-quarters performance. Fully assembled and ready to install, this upper is an ideal solution for pistol or SBR configurations where compact size matters. At the core is a 300 Blackout barrel, optimized for strong performance in shorter barrel lengths while maintaining excellent energy and versatility with a wide range of bullet weights. The compact design makes it well-suited for suppressed or unsuppressed setups. The M-LOK free-float Mfg: One Horse