The .38s are really .36s (0.357 to 0.359 inch and occasionally 0.360 inch) -- except for the .38-40, which is a .40 (0.400 inch).
Some old .44s, IIRC, are .45s -- but I'd have to look this up to be sure. The .45 handguns are 0.452-0.454 (occasionally higher), but the .45 rifles are 0.457-0459 inch and carry designations .45, .458, .460, etc.
The .40s' bullet diameters are all over the place.
For rhyme, read good poetry.
For reason, study logic.
For cartridge and caliber designations, just learn 'em or leave 'em be -- whatever they are.
