Crazy Caliber Names

[Swifty Morgan]

Does anyone here know--I mean really know--why so many calibers are wrong? What I mean is that the nominal calibers are not the actual diameters of the bullets. Some are close to nominal, but some are so far off, you wonder what the reason is.

Seems like it's just as easy to print ".357" on the box as ".38."

Examples:
.45 ACP = .452"
.17 HMR = .172"
.38 = .357"
.22 = .223"
.44 = .429"
.50 BMG = .510"

 

[Jim Watson]

There are many different reasons.
Reason #1, many calibers are, or were, named by their bore diameter. Now I realize that the groove diameter is often called the bore diameter on the internet, but that does not make it right. If, in your last example, you bore a half inch hole in a bar of steel, .500", and cut rifling grooves .005" deep, then you have a groove diameter and bullet diameter of .510". Most metric calibers are stated for bore diameter, like 7.62mm = .300" with .308" grooves and bullets. One maker calls his .300" bore rifle a 7.82mm for bullet diameter.

Reason #2, some calibers were named by their case diameter, usually because they had a heel bullet the same bearing surface diameter as the brass, and going down a barrel of that groove diameter. The .357 Magnum is based on the .38 Special, which was based on the .38 Government/Long Colt. The .38 LC with a case diameter of nearly .38" had a heel bullet of the same diameter, inherited itself from the conversion of percussion revolvers made for .376"+ balls. But then S&W went to inside lubricated bullets, the INSIDE diameter of the case, .358". They kept the case diameter and reduced the bullet and barrel. The big soft .38 LC bullets would swaged down safely, hence the early marking, ".38 Government and S&W Special."

Reason #3, two digits. Why try to remember .172 or .452 when you can just say "seventeen" or "forty-five"?

Reason #4, advertising. The .22 centerfires were standardized at .224" groove and bullet diameter pretty early on. But you have to identify your product, so .218 Bee, .219 Zipper, .220 Swift, .221 Fireball, .222 Remington, .223 Remington, .224 Weatherby, and .225 Winchester ALL take .224" bullets. But .22 Hornet (early), .22 Remington Jet, and .22 Savage High Power do not. The Hornet and High Power are older than the .224" convention and the .22 Jet was designed to shoot with either the centerfire or a .22 long rifle conversion insert or spare cylinder.

 

[Swifty Morgan]

I wasn't optimistic about hearing from someone who actually knew anything, but you came through. Thanks.

 

[jmr40]

There have been many different ways of naming them over the years. At one time some cartridges were measured from the OUTSIDE of the case. For example many 38 caliber cartridges. The bullet inside the case was .357, but the outside diameter of the case is .380.

There has never been a consistent pattern that everyone used.

 

[PapaG]

I like to mess with my buddies and talk about my .355 auto, my .43 magnum, my .308-30, and my 67 gauge shotgun.
Of course I refer to my 4X4 Silverado as my Chevy 16. (Eliminates the math)

 

[Englishmn]

460s&w = .452"
Its all marketing 460 S&W sounds better than 11.5x46R.

 

[WestKentucky]

Part of the name game is one-up-smanship at its finest. Clearly .224 has to be better than .223 right...? Not far from the urination competition between Ford/Chrysler/GM...351 has to be better than 350 and 305 is a touch better than 302. Then you see the surnames tacked on, whisper, blackout, Valkyrie, again not unlike hemi, Cleveland, HO

 

[bikerdoc]

I have seen some foreign 357 marked 9X33


I like it.

 

[Klint Beastwood]

Id like to give an example of .308 being the bullet diameter and the bore being .30 in diameter but that’s not really true...a lot of barrels are all slighting different tolerances...but usually something like .302848389294747829294747 or something stupid like that. So a 300 win mag and a .308 use the same bore diameter (across the rifling) just one is measured at that and the other is the bullet diameter...
It gets weirder when taking say a 7.62x54r and it being more a .311 bullet not a .308....

 

[Jim Watson]

The MN was originally known as the Three Line Rifle where the line was 1/10 inch. So the bore was intended to be .30" with deeper grooves than we use.

 

[Klint Beastwood]

The MN was originally known as the Three Line Rifle where the line was 1/10 inch. So the bore was intended to be .30" with deeper grooves than we use.

Yep.

 

[burrhead]

And I thought we were going to talk about things like P O Ackley's .22 Eargesplitten Loudenboomer.

 

[Jim Watson]

It's just another .224".

He also made .23 caliber barrels and bullets for small caliber hunters in states with a "larger than .22 caliber" requirement for big game.

 

[JWF III]

There have been many different ways of naming them over the years. At one time some cartridges were measured from the OUTSIDE of the case. For example many 38 caliber cartridges. The bullet inside the case was .357, but the outside diameter of the case is .380.

There has never been a consistent pattern that everyone used.

Not saying that is wrong, because the heeled bullets, and the timeline of which came 1st, I’m not sure of. But what I’d always been told, by several people, is that the .357 bore was standardized in black powder days for the .36 caliber percussion revolvers. And when they were converted during the transition period, it was easiest to bore the cylinder out the extra bit to make up the difference the case made.

Again, I don’t know which is right. That’s the 1st time I’d heard that version. But they both are plausible ways to come to the same conclusion.

Wyman

 

[wally]

When you said crazy caliber names I immediately thought of 5.75 Velo Dog


As has been said there is plenty of ambiguity as to exactly where to measure the bore diameter, then don't forget that the bullet generally has to be at lease 0.001 oversized to get a good seal.

 

[Jim Watson]

There is no ambiguity as to exactly where to measure bore diameter. There is bore diameter and there is groove diameter and the Internet Experts calling groove diameter the "bore" does not make it right.

Bullets do not have to be at least .001" oversized. The American custom is to make jacketed bullets fill the grooves and lead bullets a bit over. There are European rifles with bullets under groove diameter on the theory that the jacket metal displaced by the lands needs someplace to go. Paper patched lead bullets over black powder were usually of bore diameter, meant to upset into the rifling under the impulse of powder ignition.

The Velo Dog is French, you can't explain the French.

 

[entropy]

again not unlike hemi, Cleveland, HO

Those are all descriptive; Hemi (Hemispherical head) Cleveland (where that particular engine was manufactured, as opposed to Windsor, Ontario) HO (High Output, compared to the regular engine). I guess you could say Whisper and Blackout could be attempts at description (Both rounds were developed for use with silencers), Valkyrie; well it just sounds cool.

 

[Mk VII]

When Winchester were ready to market their version of the not-quite-standardised-yet 7.62mm NATO case they had to give it an inch-system name to increase the changes of acceptance by the market. They decided to call it .308 Winchester, probably because they already had a .30 Winchester Center Fire.

 

[Jim Watson]

And the British .30 Super had to be called .300 H&H Magnum to get any sales here.

 

[Mauser lover]

Of course I refer to my 4X4 Silverado as my Chevy 16. (Eliminates the math)

HA! If I had coffee in my mouth, it would have ended up on my screen! You sir, have tickled my funny bone today. Probably only because I'm a little tired, but I still liked it!