GT,
Contrary to the popular myth, the barrel caliber and groove dimensions in the original Parabellums do not vary much, they were held to tight tolerances.
Bore and caliber both properly refer to the diameter between lands. This because the bore is the original hole bored in the barrel before the rifling is cut. The caliber refers to the size of ball that can be passed through the barrel without being cut by the rifling, in other words the same as the bore. (Except in muzzle loading cannons where caliber is length of the barrel divided by the bore, a ratio, and has nothing to do with the size of the bore and more to do with how long the piece is.)
The American 357 as in 357 Magnum refers to the groove diameter.
To further the confusion, the 30-06 is a 30 caliber but the 308 is also a 30 caliber with the exact same dimensions. Both take a 308 bullet. You will go nuts trying to make sense of cartridge designations.
|