May 13, 2007, 02:33 PM
how are they determined?
For example, why is the .22 a .22 and not .20 or .25?
And what about the thousandths like .223, .308, 7.62, etc.?
Thanks in advance.

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May 13, 2007, 02:35 PM
most are completely arbitrary and capricious , at best, just a name for a round, unlike the other makers name for the same round. some are accurate desc, of either the diameter of the bullet, or the diameter of the bore of the bbl, minus lands, or diameter of the bore, plus lands.

May 13, 2007, 02:36 PM
Whoever designs them measures them and usually rounds the number to two or three decimal places, same with metrics.

May 13, 2007, 02:41 PM
Basically caliber is bore diameter in hundredths or thousandths of an inch, or milimeters in hundredths, but there is some "artistic freedom" as to its use in cartridge designations. A 30-30, 30-06, 308 and 300 win mag all use a near .30" bore with .308"dia bullets, the metric conversion would be 7.62mm=.30"
there are some calibers where there may be more or less accuracy in bullet or bore, standard bullet dia for a 44mag is .430, 45acp is .452, 223rem=.224 and so on.

more or less the formula is (approx caliber) then (charge weight, year of entry into US service,intended use, cart or firearm make, or advertising buzzword) such as 45-70=45 cal 70gr charge, 30-06=a military cartridge, 30cal bore adopted in 1906, 308winchester =.308 dia bullet originally loaded by winchester, 45 Automatic Colt Pistol, or even 22 earghesplitten loudenboomer (a real although limited production cartridge.

May 13, 2007, 05:35 PM
In short, approximate bullet diameter and differentiation between cartridges of like caliber. For the record, there are multiple 20 and 25 caliber cartridges out there.

The Lone Haranguer
May 13, 2007, 07:15 PM
Sometimes they just want to give it a catchy name. For example, the .222 Remington is not actually .222" caliber (and neither is the .223), but it caught your eye, didn't it?

May 13, 2007, 07:26 PM
Kind of like engines. They'll call something a 350 but it's really a 346ci. ATV makers do this a lot also. In some ways it can simplify things until you get out the micrometer and start actually getting into the precise measurements.

May 13, 2007, 09:43 PM
And the 7.62mm X 39mm is actually 7.9mm (.311" diameter bullet), whereas the 7.62 Nato is actually 7.62mm (.308" diameter bullet, as noted above.)

Then there's the .45 ACP, the .45 Colt, and the nonexistent .45 Long Colt (Although some ammo manufacturers have actually started to use this designation.)

And the .380 ACP is also called the 9mm Corto and the 9mm Kurz. This is to distinguish it from the 9mm Makarov and the 9mm Luger.

("Corto" and "Kurz" both mean "short" in Italian/Spanish and German respectively.)

The Cartidge, Ball, cal .30 Pistol, was a rifle round to be used in the "Pedersen Device" conversion for the Spingfield '03 rifle.

Some Luger pistols were actually gauged as to actual bore diameter, and can be found with the various diameters stamped on the barrel. Why the Germans did this I do not know for sure, but I suspect an answer may be found in some of Sigmund Frued's writings.

Just to make you feel better, I point out that Hatcher's Notebook, in the edition of 1947, had nine pages devoted to the variations in naming, bullet diameters, groove diameters, and other anomolies in cartridge nomenclature.

The situation has gotten worse since 1947, with all the new cartridges.

And "caliber," in artillery usage, refers not to the diameter of the shell or bore, but to the length of the barrel divided by the shell diameter, as in 16"/50. This meant that the barrel was 800 inches, or 67 feet long.

Sorry. Couldn't help myself. I'm sure there's more fun to be had in cartridge naming, but I'm done for now.

May 14, 2007, 07:33 AM
I was unclear. I understand how rounds are *named*, what I want to know is when whoever it was sat down at his drawing board to design the .22, why/how did he decide on .22", not .21 or .23?
Thanks again.

May 14, 2007, 09:25 AM
OH, Well I think basically the desire to create a superior cartridge. Weither one that is optimized for a single purpose, or one that is designed to be extremely versatile. Gunnies come from the same mold as the wright brothers, Karl Benz, thomas edison and most other tinkers, inventors and people generally dissatisfied with most material objects. You won't have much left if you hunt squirells with a 45-70, and hunting elephants with a 22LR is not a very good idea. It was difficult, before the industrial revolution to drill a small bore in a long barrel due to torque deflection, and hammering over mandrel was inconsistent in smaller calibers, and black powder does not burn slow enough to push a small bullet to high velocity without blowing up the chamber. Some are centered around the machining process, a 1/4" bit will drill a .250 dia hole, when reamed and rifled the groove dia is approx .257 and that is the dia bullet used in a 257 roberts, 25-06, and 25 wetherby. Gunsmiths also have near half a millenia of tradition to draw upon for inspiration, and can make design changes incorporating aspects of much loved traditional cartridges, as in 45 colt, 454 casull and 460S&W. If a cartridge works well in its original development, say a 30-06 that replaced the 30-03 that replaced the 30-40krag, then the tinkerers might try a larger bullet like the 35 wheelen, or a smaller one like the 25-06 to either push a heavier bullet, or to increase velocity. basically there are few things in the world of arms that someone hasn't tried.

May 14, 2007, 09:46 AM
There's also a lot of history and "inertia" behind these decisions; when the manufacturers were switching over to smokeless powder, inside-bulleted cartridges (which use smaller-diameter bullets, though at a faster velocity, than the older black powder cartridges they were developed from), they didn't want to unnecessarily confuse people with the facts. So, a ".38" stayed as a ".38", instead of being renamed as what it actually is, a ".35". (the CASE dimensions stayed the same, but they switched to a smaller-diameter bullet that goes inside the case, instead of a heel-based bullet that has a base that's crimped into the mouth). If someone today came out with a brand-new cartridge called the "11.43x23", I doubt anyone would buy it, but that's just because they know and are comfortable with the name we already KNOW that cartridge by, the 45 Auto.

May 14, 2007, 11:34 AM
Snatch up a round, grab a micrometer (english or metric) and enable your imagination.

May 14, 2007, 12:17 PM
The basic thing to remember is that calibers are names. They traditionally include a measurement of some sort, but are not a measurement in and of themselves.

Unless you are familiar with the specs of the cartridge, you cant really tell how powerful it is, or if it's a pistol or rifle cartridge, etc.... etc....

The number used in the name is typically one of several measurements:
Bore diameter
Groove diameter
Nominal bullet diameter
Case body diameter

Also, in the case of NATO and other cartridges, if you see a "x__mm", it refers to the case length. (9x19mm, 5.56x45mm, 7.62x39mm, 7.62x51mm, 7.62x54R <--- The "R" means rimmed)

And that's basically the whole issue in a nutshell, its all tradition and marketing basically.

May 14, 2007, 12:46 PM
whoever it was sat down at his drawing board to design the .22, why/how did he decide on .22", not .21 or .23?

I think the true diamater of a .22 bullet is .224". Maybe he just rounded it off. Other rounds need to be named different to distinguish them apart even though they may use the same bullet diameter (or same bullet for that matter). There are rounds like .22lr, .22 short, .22 mag, .221, .222, .223, 22-250, etc.

May 14, 2007, 03:54 PM
"Thirty-six special" just doesn't sound right.

Can you imagine singing: "back on the range once more, totin' my old forty-three" ...?

Or going out to shoot tin cans with your "twenty" ??? ;)

May 14, 2007, 03:59 PM
Just don't do what some "newsies" do and call a 22 cal. a 22mm!!!!

May 14, 2007, 04:11 PM
whoever it was sat down at his drawing board to design the .22, why/how did he decide on .22", not .21 or .23?

That's an interesting aspect of the question. Most of the decsion process relates to the usage that the cartridge designer has in mind. Obviously you don't hunt bear with a .22, or squirrels with a .44 Magnum.

Some of it has to do with the materials or processes at hand. Rifling a Pennsylvania or Kentucky rifle in .22 caliber with the single-groove cutters of the day would have been next to impossible, at least on any kind of economical basis. So many of these "squirrel guns" were .36 caliber, which is about the minimum size for a cutter head assembly in those days, it would seem, just looking at the dimensions involved.

I tried to do some quick research on this. One thing I came up with was an article on the .22 Hornet, whose bullets were originally made from re-forming .22 rimfire cases. So that's what decided the final dimensions of the .22 Hornet bullet.

I made 6 mm bullets out of fired .22 Magnum cases once (when I had my machine shop.) In that case, the process was reversed. I had a 6mm rifle --now, what can I make bullets out of? Lo! 22 Mag case are ideal!

Here's a history of the .22 cartrdige, for what it's worth --although it gives no insight into Flobert's decision process.

Maybe the choice of ".22" was dictated by what round shot sizes were cheapest at the time. "F" shot size happens to be .22 in diameter. Maybe Flobert had a sack of "F" shot and decided to tinker around with it. And that may be the sole reason for the choice.

For all we know, the .243 Winchester dimensions came about because Winchester had a bunch of Letter "C" drills (0.242") around....

...which begs the question of why a Letter "C" drill is .242 inches. Who knows? Perhaps, in days of yore, some machinist said to his assistant, "I need you to grind a drill bit which is about this big, see?" and he held up his thumb and forefinger and the dimension his assistant obtained between his boss's fingers was .242 inches.

Thus the "See" drill got corrupted to "C." ;)

May 14, 2007, 04:23 PM
IIRC the 22 caliber was the original brass cased round due in part to the Primers for Cap and Ball revolvers being .22/100ths of an inch. Smith and Wesson again IIRC added lead to the primer and made a revolver that fired their new round.
According to a cursory search of Wikipedia the 22 short was in fact the first American Metalic Cartrige designed for the S&W revolver. No verification of the fact that the cap and ball revolver took a 22 cal primer but That seems to be a Factoid I remember from "Tales of the Gun" Don't quote me on it, I want to qualify it's veracity.

Add on:
Here is a Wikipedia Quote and a link to the original page.

The first rimfire cartridge was the .22 BB Cap, which used no gunpowder by relying entirely on the priming compound for propulsion. Dating back to 1857, the .22 BB Cap is essentially just a percussion cap with a round ball pressed in the front, and a rim to hold it securely in the chamber.

May 14, 2007, 06:15 PM
I see we've managed to avoid part of the suffix issue.

Depending on what terminology was in vogue at the time, the suffix can mean different things.

For example, .30-06 is the .30 calibre cartridge adopted in 1906, while the .30-30 cartridge is an alternative name for ".30 Winchester Center Fire" adopted by those who didn't want to sell their gun, say "Marlin," chambered for a "Winchester" round. The .30-30 is a .30 cal round over 30 grains of (black?) powder, and was the first expressly smokeless cartirdge. The ".30-30" designation stuck in part, I believe, due to its being easier to say "thirty-thirty" than "thirty-double-you-cee-eff."

It gets better, of course.

We have the ever-popular ".38" which is mostly understood to mean ".38 special" (a sensible name for a .357 round). It's one of the more popular chamberings for revolvers made by, oh, Smith & Wesson. Ironically, the ".38 S&W" cartridge is NOT the same thing, and the rounds are not interchangeable.

Ahh, nomenclature.

It is my favorite thing.

May 14, 2007, 07:42 PM
Wait a second. Are you saying I can't chamber a .38 S&W in my .357 Mag?

I was sure that I had read somewhere that I could...? It is very possible that I could be wrong.

May 14, 2007, 07:58 PM
Wait a second. Are you saying I can't chamber a .38 S&W in my .357 Mag?

You can safely chamber and fire a 38 S&W SPECIAL in your .357, but a 38 S&W is a larger-diameter cartridge that won't fit either a 38 Special or 357 Magnum chamber; this is one of the things that goes into deciding what to call a new cartridge, since you don't want to encourage unsafe gun/ammunition combinations.

May 14, 2007, 08:37 PM
NO!!! 38 S&W has a bullet dia of .361, case dia of .386, but 38special and 357mag bullets are .357 or .358 in dia with a case dia of .379

but, just for confusions sake 44S&W (AKA 44russian), 44 special and 44 mag can all be safely fired from a 44mag.

but never ever try to fire a 38super automatic out of a pistol chambered in 38 automatic even though both cartridges are dimentially identical

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