On Tue, 7 Nov 2017 07:54:36 -0800 (PST), rangerssuck
wrote:

The recent argument over .223 and 5.56 in another thread has reminded me of a question that's been lingering in the back of my mind for a while: Where do these oddball sizes come from? I understand (pretty much) what they mean, but what the hell, did somebody wake up one morning and decide that .22 (and where did THAT come from) is like a tenth of a percent too small, so I'll start manufacturing .223?

It's a long history of completely arbitrary choices. Some have been
based on bore diameter at the lands; others on bore diameter at the
grooves (which usually is the same as bullet diameter); others have
just been plucked out of the air.

A .38 Spl. bullet is actually .357 bullet and groove diameter. That's
the same as a 9 mm. Etc. Etc. The .38 Spl. is named for the diameter
of the case neck. sigh

Sometimes they just bumped an existing caliber designation up to
signify a new cartridge. For example, the .223 followed the .222
Remington Magnum (Wikipedia said "222 Remingon Special." I'm pretty
sure that's a mistake.) It's basically a revised version of the .222
Rem. Mag. -- one of my favorite varmint cartridges, although not quite
as accurate as the smaller .222 Remington.

As for the arbitrary ones, there was the .218 Bee and the .219 Zipper,
both introduced by Winchester in the same year, but each made for a
different model of lever-action rifle. They both shoot the same
..224-in.-diameter bullet. The Zipper was a much hotter cartridge.

Then you have the year of introduction: .30-03 and .30-06. And the
necked down (or rarely necked up) versions of earlier cartridges:
..22-250, .25-06, 7mm-08, 30-378 Weatherby Magnum.

In other words, it more or less means nothing. g


Or did someone turn some stuff on his lathe and measure it afterwards?

No.


There MUST be some interesting stories in there somewhere.

There are. There are entire books written about some of them.


PS: The only things I have fired a
22 (why not 20 or 25?)
38 (why not 35 or 40?)
177 pellet (why not 175 or 200 or even 180?)
9mm (because 8 was too small and 10 was too big?)

Long stories, some of them interesting.

--
Ed Huntress