GLOCK 17 GEN 4 METAL VERSION GBB At the 2010 SHOT Show, Glock presented the “fourth generation”, now dubbed “Gen4” by Glock itself. Updates centered on ergonomics and the recoil spring assembly. The initial two fourth-generation models announced were the full-sized Glock 17 and Glock 22, chambered for the 9×19 mm Parabellum and .40 S&W cartridges, respectively. The pistols were displayed with a modified rough-textured frame, grip checkering, and interchangeable backstraps of different sizes. “Gen4” is roll marked on the slide next to the model number to identify the fourth-generation pistols