Firearms Chambered in .45 ACP (Submachine Gun)

The Heckler & Koch UMP (Universale Maschinenpistole, 'Universal Submachine Gun') is a blowback-operated submachine gun developed by German manufacturer Heckler & Koch in the late 1990s. Designed as a lighter and more cost-effective alternative to the roller-delayed HK MP5, the UMP is chambered primarily in .45 ACP, though versions in 9×19mm (UMP9) and .40 S&W (UMP40) are also available. It features extensive use of polymer for the receiver and furniture, a side-folding stock, and Picatinny rails for accessory mounting. The UMP has been adopted by various law enforcement agencies and military units worldwide.

The M3A1 is a .45 ACP submachine gun developed by the United States Army during World War II. It was designed as a cheaper and faster-to-produce alternative to the Thompson submachine gun. The weapon earned the nickname Grease Gun due to its resemblance to the automotive tool used for applying grease. The M3A1 simplified the original M3 design by eliminating the cocking handle and using a finger hole in the bolt instead. It remains one of the most cost-effective submachine gun designs ever put into mass production.