A fire mode selector is mounted on the left side of the slide. This pistol fires in semi-auto and full-auto modes. One that raised the GLOCK 18 in my estimation involved doing an attack on principal (AOP) drill in which two team members engaged the “threats” with the G18s on full-auto while the rest of the team evacuated the principal. Unfortunately, the answer is you pretty much can’t.. Glock 18 Full Auto Switch, H4T How Do I Buy a Glock 18? GLOCK Firestorm. (This first appeared several months ago.) Hussein, bedraggled and bereft, was armed with one of the rarest of handguns: the Glock 18, the full auto Glock. Thanks to a bunch of laws (1934 NFA, 1968 GCA, & 1986 FOPA), there are only three ways of obtaining a Glock 18 (or any other machine gun):Transferable: Guns registered prior to May 19, 1986. The magazine is interchangeable with the Glock 17. While serving with one close-protection unit that was testing Glock 18s, we tried various drills. The Glock 18 is fed by a double-stack magazine that holds 17 rounds. Also this pistol can be fed from a 31- or 33-round magazine.