The submachine gun known as the Heckler & Koch UMP ("Universal Machine Pistol") was created and produced by Heckler & Koch. They created the UMP in the 1990s, and it went into production in 2000. The UMP was created to replace the MP5 as the lighter and less expensive option. Given that the MP5 was not available in the popular and widely used .45 ACP round in the United States, it was primarily created for use by American military and police enforcement forces. Despite the UMP's upgrades and cost reductions, the MP5, which ultimately outsold the UMP, remained the industry standard. The UMP is a magazine-fed, blowback-operated submachine gun that fires from a closed bolt. The weapon's closed bolt improves accuracy, but its simple blowback mechanism makes it more difficult to control than the MP5. The UMP chambered in .45 ACP and .40 S&W has better stopping power but slightly less efficiency at longer ranges. Four trigger group configurations are available for the UMP, offering various combinations of semi-automatic, 2-round burst, fully automatic, and safe settings. It has a buttstock that may be folded to the side for storage or transportation. Picatinny rails can be mounted on the top of the receiver, as well as the right, left, and bottom of the handguard. The bottom rail can be used to mount vertical foregrips for maximum control during automatic fire. The UMP is available as the UMP45, UMP40, and UMP9 (calibers .45ACP, .40S&W, and 9x19 Parabellum), as well as the USC, a semi-automatic variant of the UMP designed for civilian use.