The 9×18mm Ultra is a German pistol cartridge.[1] It was originally developed in 1936 for use by the Luftwaffe, but was not adopted at that time.[1]
In the 1972–1973 time frame, Walther introduced the Walther PP Super, chambered in 9×18mm Ultra for the West German Police.[1] It might have been influenced by the success of the Soviet 9×18mm Makarov, although most observed the opposite (the Ultra cartridge is usually agreed to have been the design basis for the Makarov, with similar case length and a slightly wider and shorter projectile). It is often interpreted as an intermediate round between 9×17mm and 9×19mm Parabellum, fit for simple blowback pistols.[2] However, as actually loaded, the cartridge's working pressure and velocities are much closer to those of .380 ACP than to 9×19mm.
The Walther PP Super was discontinued in 1979.[citation needed] The cartridge was made available to the civilian market in 1975,[1] but did not gain lasting popularity.
In addition to the Walther PP Super, the SIG Sauer P230,[1] Mauser HSc-80,[3] and Benelli B76[1] were also produced in 9×18mm Ultra.
The 9×18mm Ultra (.355-inch caliber) is not interchangeable with the 9×18mm Makarov (.365-inch caliber), which uses a larger-diameter bullet.