One Horse 300 BLK 16" Complete AR-15 Upper Receiver 15" M-LOK

A complete 300 BLK upper that pins onto any mil spec AR-15 lower. The barrel is a 16" SOCOM profile running a pistol length gas system, which is the setup most 300 BLK builders land on because it cycles supersonic and subsonic loads without much argument. The heavier profile also holds up better across longer strings than a pencil barrel.

The handguard is a 15" free float M-LOK design with a full length Picatinny rail on top for optics and backup sights, and it covers nearly the whole barrel. A nitride bolt carrier group is included. Bolt it to a lower and the rifle is finished.