The 7.63x25mm Mauser (.30 Mauser Automatic) round was the original ammunition of the Mauser C96 service pistol. The basis of this cartridge was the 7.65x25mm Borchardt cartridge of 1893, the only successful automatic pistol cartridge in production at the time. The 7.63 mm Mauser is sometimes confused with the later 7.65x22mm Parabellum (.30 Luger), also a bottlenecked pistol cartridge.
The 7.63 mm Mauser cartridge was the basis for the 7.62x25mm Tokarev round adopted by the Soviet Union. Although the case dimensions of the two cartridges are nearly identical, the 7.62 mm Tokarev has a stronger powder charge and is not suited for use in C96 pistols or other firearms chambered for 7.63 mm Mauser.
Firearms chambered for the 7.63 mm Mauser cartridge include the Mauser C96 and variants and copies, the Astra Model 900 and variants, and a handful of pre-World War II submachine guns such as the Swiss Bergmann M/20 exported to China and Japan.
During the Finnish-Soviet Winter War and World War II, the cartridge was issued by Finnish and German forces for use in captured Soviet submachine guns, due to its inherent substitutability for the Soviet 7.62x25mm round. According to Finnish military archives, the Finnish Army ordered one million rounds of 7.63mm Mauser from FN for this purpose.