The bore is the land to land diameter. many people incorrectly use it to mean the groove to groove diameter. It is the diameter the barrel is "bored" to before the rifling is cut.
The caliber designation also refers to land to land diameter but is abused as often as the term bore.
Cartridge designations have even less to do with diameter. They have more to do with what looks good in the advertsing copy.
The 38 S&W does not have the same diameter as the 38 Special which does have the same diameter as the 357 Magnum, the 357 Supermag, the 357 Maximum, and the 360 Dan Wesson. Just to confuse the issue even more, if you have a Dan Wesson 357 Supermag, chambered for the 357 Supermag, it will say 357 Maximum on the side, a different cartridge. Go figure.
The 44 S&W does not have the same diameter as the 44 Russian, 44 Special, 44 Magnum, and 445 Supermag, all of which have the same diameter.
The 45 Colt has a groove diameter of .454 or .451 depending on whether it was made before or after WWII. And it's not the "45 Long Colt" although there is such a thing as the 45 Short Colt. (The 45 Short Colt and the 1909 Colt 45 share the distinction of today being the two most obscure cartridges the US Army ever issued.)
Bottom line is you just have to go dig and find out what its really supposed to be. And take that with a grain of salt.
I'd hesitate to call Luger barrels oversized anyway, it's the original barrel and hence all others are copies of it.
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