 The weapon has an additional tungsten weight on the bolt to slow the rate of fire, which would otherwise make such a lightweight weapon uncontrollable.The 9 mm Parabellum Glock 18 is a select-fire variant of the Glock 17, developed in 1986 at the request of the Austrian counter-terrorist unit EKO Cobra.This machine pistol has a lever-type fire-control selector switch, installed on the left side, at the rear of the slide, serrated portion (selector lever in the bottom position for continuous fire, top setting for single fire).