WELROD Mk.I (A&B) 9mm Parabellum Cartridge.
The 9mm. Luger, also known as 9 mm. Parabellum or 9X19 NATO was introduced in 1902 with the German Luger automatic pistol. It was adopted first by the German Navy in 1904 and then by the German Army in 1908. Since that time, it has been adopted by the military of practically every non-Communist country. It has become the world's most popular and widely-used military handgun and submachine gun cartridges.
In 1985, the 9 mm. Luger was adopted as the official military cartridges by the U.S. Armed Forces. It is now in use with most of the militaries of the world, including all of the NATO countries. The 9 mm. Luger cartridge is produced by all major ammunition makers in a wide variety.
The cartridges case is rimmed with a slight taper from rim to mouth (see illustration) which enhances feed reliability. It uses a .356-inch diameter bullet.
Illustration courtesy of Mike Haas.