9mm v .30 luger

[Edward Tinker]

never a dumb question.

only by the size of the bore. That said, the 7.65mm (or 30 luger) will go into the front of the barrrel, while a 9mm will not fit into a 30 luger.

You can "usually" tell by a picture and in real life fairly easy to tell.

Also, both cartridges will fit in the same luger magazines, and are interchangeable.

Ed