[sigstoat]

> In particular, wrt physical dimensions, my - probably naive - take is that (radius x length) seems to go quite a long way in describing a bullet.

that doesn't describe much of a bullet, and nearly nothing about a caliber.

you can take a look at the SAAMI specs and get a sense of what goes into such things.

https://saami.org/technical-information/cartridge-chamber-dr...

the popular name of a caliber is exactly that, a name, and describes the caliber about as well as "John" describes a human being.