Study Identifying Luger Caliber: .30 Luger or 9mm Luger?

[flydive]

Originally Posted by lugerholsterrepair

Was there a specific time when the switch occurred from 7.65 x 21mm (.30 Luger) bottleneck cartridge to the 9 x 19mm Parabellum cartridge? Yes, almost immediately after George Luger invented it.

Was this transition across the board (did all manufacturers change simultaneously)? Yes, since there was only one manufacturer, DWM.

The 7.65(.30 Luger) was in production till 1947, so there were no switch as such, but parallel production.