The American 180 is a .22 rimfire submachine gun that fires at 1200-1500 rounds per minute or more, and feeds from drums of 177 to 275 rounds capacity. While it makes a great recreational machine gun, it was actually initially developed with law enforcement sales in mind. The notion was that the .22LR cartridge posed a minimal danger of overpenetration and was extremely easy to control, and the many repeated hits that could be made with the American 180 would make up for its lack of ballistic effectiveness. And that’s not necessarily incorrect.
Several law enforcement agencies did actually buy the guns, and one police shooting involving one is documented, from 1974. It never became really popular with police agencies, though, and production basically ground to a halt in 1986 when it became impossible to manufacture new machine guns for the civilian market.