I know what you are trying to say to Lunkerdog. But you are the one who is wrong here. The caliber represents the diameter of the projectile. And, for the 30 calibers, that's .308 inches. Or, .308 caliber.
Ummm... I guess at this point about all I can do is refer to my manuals... What your saying is true in some but certainly not all cases.
Here's a few examples... All of the .308's are listed under the heading .30 caliber... The .270's are actually .277 in diameter... The .35 calibers are .358 in diameter... The .44 calibers are .429 in diameter.
The American system is actually a bit screwy when listing cartridges... For example the 30/30 was meant to represent a 30 caliber loaded with 30 grains of a certain powder (I can't remember which powder) The .30-06 represents a .30 caliber cartridge that was developed in 1906, that due to performance pretty much replaced the .30-03 which was a .30 caliber cartridge that was developed in 1903.
The European system is a bit more cohesive as it designates a cartridge in milometers based first on bullet diameter then case length... For example the 9mm Luger (Parabellum) in the European system is designated the 9x19. While our .380 American designation is a 9x17 in the European designation.
We know that all. 30 calibers are .308 in diameter, but in the end they fall into the .30 caliber family of cartridges.