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

[mrerick]

Here are some illustrations to help with identifying the caliber your luger was made in.

The original Luger cartridge was the .30 Luger (7.65x21mm Parabellum), a bottleneck cartridge. The chamber that this cartridge fits into has a stepped shape that supports the bottleneck.

The 9mm Luger (9mm x 19mm Parabellum) cartridge has a similar cartridge base, and does not have the bottleneck. This is why the one Luger magazine design can work with both cartridges.

Several posts mention the "pencil test". The fact is that a hex shaped (sharp edges) No. 2 pencil Will snugly fit down a .30 Luger caliber barrel. A round No. 2 pencil generally will not fit down the .30 Luger barrel.

Both pencils will loosely fit down a 9mm Luger barrel.

The pictures attached to this post are annotated.

They first show a 9mm cartridge placed in a .30 Luger barrel's chamber. It will NOT fit properly into this chamber, and would do damage if it went off (photos are of a dummy cartridge). It will stick out of the chamber, and the toggle train will not go into battery.

Next, pictures show how a 9mm Luger round will rest on the end of a .30 Luger barrel, and a 9mm Luger barrel.

Next, a Hex No. 2 pencil fits tightly into a .30 Luger barrel, and a Round No. 2 pencil rests on top of the .30 Luger Barrel.

Next, a Hex No. 2 pencil fits loosely into a 9mm Luger barrel, and a Round No. 2 pencil fits loosely into a 9mm Barrel.

Hope that these help you identify the caliber of your Luger!

Marc