Quote Originally Posted by Patrick Chadwick View Post
As to the bore diameter, surely it is quite simple to stick a 9mm bullet in the muzzle, twiddle it around, and measure the diameter of the bright line that the muzzle will rub on the nose of the bullet?

I'm probably going to sound like a noob here, but sounding like a noob is a lot better than making a mistake and firing the wrong ammo.

Is it really that simple? How accurate does the measurement have to be? Unless I had calipers or a micrometer, I don't think I could get a very accurate reading this way, and if I had calipers, I wouldn't need to mess around with sticking a bullet into the muzzle. There are a lot of cartridges that are just a tiny bit off on the diameter but are completely different rounds. Heck there are plenty that actually have the same diameter and are still completely different rounds. I always figured the bores widened a little with use too. Maybe this will work because lugers were only made in a few specific calibers? So if it comes out somewhere close to 7.62mm i can be fairly certain I've got a 30 luger? What are the other possibilities? Do you measure a bore from groove to groove, or land to land?