Zenith Firearms ZF-300, Semi-automatic Pistol, 300 Blackout, 12 Threaded Barrel, Flash Hider, Matte Finish, Black, Polymer Grip, Manual Safety, Free Float M-LOK Handguard, 30 Rounds, 3 Magazines ZF300BKOUT12 The ZF-300 12" is a semi-auto pistol with a roller-delayed blowback operating system. This pistol is chambered in 300BLK and comes with a full length Picatinny rail, & a cold hammer-forged barrel. The American Made ZF-300 also features a last round bolt hold open system. This firearm features a buffer tube compatible end cap.