Umarex Glock 17 Gen3 Air Pistol, 177 BB, 350 Feet Per Second, Black Finish, Blowback Action, 18Rd 2255208 The GLOCK G17 GEN 3 is the blowback BB repeater you have been waiting for. Powered by easy and affordable 12 gram CO2, the G17 GEN 3 is just right for holster drills, target practice, or backyard plinking.