Hello, I would advise against shooting 9x19 in an unmodified 9x21 gun. The 9x21 was mainly designed to provide Italian civilian shooters with an alternative to the 9x19, which is only allowed for the military and law enforcement over there. Although the performance of both cartridges is very similar their dimensions are obviously not. It is however possible that the barrel may be modified to accommodate the 9x19. You may want to raise this question in the Beretta forum, where there are some Italian members.