Rifle = 458 but Pistol = 452 ?

[Willyp]

Why are bullets for a 45 caliper rifle .458 but for a 45 caliper hand gun they are .452 ?
No one seems to no the reason!

[17nut]

If you had asked why a .38spl is'nt .38 i could have answered.
Or why a .36 cap and ball isnt .36.

[Good Cheer]

I know I know!

It's because pistol boolits are light weight and need a paper patch in a rifle!

[Artful]

Why are bullets for a 45 caliper rifle .458 but for a 45 caliper hand gun they are .452 ?
No one seems to no the reason!

Hmmm, Colt SAA .454, but Colt 1911 .451, Bushmaster AR in 45 Bushmaster cartridge .452, Winchester Model 70 .458 Magnum, AR's in .458 SOCOM,
45-70 up to .462 in trapdoors in my records.

Guess it's because they had barrels on hand in those Diameters.

[NSB]

It's very simple.....there are no regulations requiring any firearm manufacturer to hold any specific tolerance on any barrel diameter. It's simply their choice as to what diameter they use. In today's world they are better at standardizing diameters for most new calibers, but not always. A good example of variation for no reason at all is in 50cal muzzle loaders. About every manufacturer uses a slightly different diameter that's "close" to fifty caliber. That's why they make so many different sabots. As far as .45 cal handguns go, it's not even .452. Look at most 45ACP bullets, they're .451 while the Colts are .452. It's goofy, but that's simply the way it is.

[dragon813gt]

Why does the 327 Federal use .312 bullets? Answer.....because that's what the manufacturer says it uses. Technically 45 caliber can cover a broad range of bullet diameters. It's more annoying when you have different handgun and rifle specs for the same cartridge like in the case of the 44 Magnum.

[JimB..]

In the old days did the gun makers also produce ammunition? Bring out a new gun and matching ammunition as a competitive advantage and incremental revenue stream?

[Tackleberry41]

Ever try to explain some of this to a non gun person? Good luck. There is no rhyme or reason to it. Seems alot of it was just pulled out of someones....

Why is 44 mag actually 429, why not call it the 43 mag?
Why do 44 cal muzzle loaders use 451 cal bullets?
Why didnt they make the 45 acp the same as the 45 colt vs 451 and 454?
But then rifles were 458?
38 special wasnt anywhere near 38, why not 36 special?
Doubt anybody can give a straight answer on any of it.

[Der Gebirgsjager]

I guess you'd have to have been there at the time to know for sure, but my speculation would be that the diameters of a .45 Colt and a .45-70 are different because they were developed independently from each other. Unlike the .357 mag. which originated from the .38 Spec., the diameters of the .45s were from completely different projects. There were no standards at the time, like SAMMI today, so the designers were free to call anything that measured between .44 and .46 a .45. And as illustrated in a couple of posts above, to some extent that holds true today. Had the .45 Colt been lengthened into a rifle cartridge the diameter would have remained the same.

[Ballistics in Scotland]

Revolvers and rifles on both sides of the Atlantic tended to have rifling about .004 to .005 while rifles needed .008in. because of their greater pressure and velocity. I don't know why the .45ACP got a smaller diameter, but I think the hot favourite explanations have to be needing less rifling depth with the jacketed bullet, or the use of a particular lot of .30-06 or Mauser cases in development of the cartridges. Later Colt and others fell in with the automatic dimensions for their previously .454in. .45LC revolver cartridge.

[Texas by God]

Blame it on the Ordnance Dept. circa 1872 when the .45 Colt and 45-70 Govt. were being developed. I guess they got it right because both cartridges are more popular than ever.
Best, Thomas.

[RPRNY]

Because the pistols weren't originally. "45 Cal" was simply a redesignation of 44 Cal when cartridge bullets were introduced in pistols. "44 Cal" cap and ball revolvers had .452" grooves (+/- .002") but .446 - .448" bores. So, they weren't the same to start with. 45 Cal rifles were .450 (+/- .002" or so) bore in the muzzle loader days (.456" - .458" grooves) and that carried over to cartridge rifles.