There are plenty of AR15 Upper Receivers on the market, and if you're looking for a pistol upper receiver chambered in .300 AAC Blackout, check out Primary Weapons Systems MK109 MOD1-M. With a 9.75-inch barrel, it is the perfect size for a home defense weapon and a fun range gun, and .300 BLK packs a lot of punch that is satisfying to shoot. Plus, the MK109 MOD1-M comes with the Primary Weapons Systems Triad 30 muzzle device and their long-stroke piston system, so you're ready to roll as soon as you install it on the lower receiver. It even has Picatinny rails and M-LOK attachment points along the handguard, making it the perfect choice if you want to add attachments and optics. MK109 MOD 1-M Upper, 9.75in Barrel, .300BLK 3 setting Adjustable Gas Regulator, PWS Long Stroke Piston System Specifications for Primary Weapons Systems MK109 MOD1-M 9.75-inch Upper Receiver: Manufacturer: Primary Weapons Systems Barrel Length: 9.75 in Barrel Twist Rate: 1-8 Muzzle Device: PWS Triad 30 Finish: Matte Color: Black Condition: New Magazine Included: No Features of Primary Weapons Systems MK109 MOD1-M 9.75-inch .300 AAC Blackout Upper Receiver: 9.75-inch Barrel PWS Triad 30 Muzzle Device Chambered in .300 BLK Matte Black Finish Package Contents: Primary Weapons Systems MK109 MOD1-M 9.75in bbl Upper Receiver