Luger ID .30 cal or 9mm

[Josafoot]

Originally Posted by DavidJayUden

Other way round. The .30 Luger cartridge is a bottleneck round, which necessitates a "step" in the chamber to correctly fit the case.
dju

As I typed that response, the engineer in me realized that it made no sense

So... I did all of my research based on the 9mm. Is there anything about the .30 cal I should know?

I am still holding out that it is a 9mm as the .30 cal ammo seems hard to locate.