7.63×25mm Mauser
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The 7.63×25mm Mauser round is a bottleneck, rimless, centerfire cartridge, originally developed for the Mauser C96 service pistol. This cartridge headspaces on the shoulder of the case. It later served as the basis for the 7.62mm Tokarev cartridge... Wikipedia
Base diameter: 9.86 mm (0.388 in)
Designer: Deutsche Waffen und Munitionsfabriken
Parent case: 7.65×25mm Borchardt
Place of origin: German Empire
Used by: Germany, Soviet Union, China, Spain and Finland