Georg Luger developed the 7.65mm cartridge from earlier 7.65 mm rounds. The 7.65mm Parabellum cartridge uses a shorter cartridge case than the 7.65x25mm Borchardt, 7.63x25mm Mauser, and 7.62x25mm Tokarev cartridges, which are the about same length.
Make sure you are using the right gauge.
Vern
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