ONE HORSE 300BLK COMPLETE UPPER RECEIVER W/SOCOM PISTOL BBL FOR AR-15 Upgrade your rifle with a versatile 16" .300 Blackout complete upper receiver built for reliable performance, modular flexibility, and consistent accuracy. Designed to handle a wide range of shooting applications, this upper performs effectively with both subsonic and supersonic loads. At the core is a 16" .300 Blackout barrel paired with a pistol-length gas system, delivering reliable cycling-especially when running subsonic ammunition or suppressed setups. This configuration enhances function across various loads while maintaining smooth operation. The 15&qu Mfg: One Horse