HK Heckler & Koch USP .177 Caliber BB Gun Air PistolCheck out this HK USP. It holds 22 rounds in a heavyweight magazine that also houses the CO2 cylinder that powers this BB pistol. It has an ambidextrous magazine release, integrated accessory rail and realistic hammer movement. This is a great practice pistol for 9mm USP owners. For just pennies a shot, you can shoot for hours. All marks used under license. (CO2 not included) 400 FPS Shoots . 177 Caliber Steel BBs CO2 powered Uses one 12 gram CO2