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.calibre

There are two primary methods of naming the outside diameter of the bullet. One is by naming it by tenths and hundredths of inches and the other is by millimeters. Sometimes these are combined with other aspects to make the full name of the caliber as well.

So, a .40 caliber means that the outside diameter of the bullet is .40 inches. A 9mm means that the diameter of the bullet is 9millimeters. Often though these aren't exactly accurate. For instance .223 NATO is actually .224" and .357 magnum and .38 special actually use the same sized bullet.

Then there are some other ones that have names with numbers based on other things.

The .30-06 (actually with a .308 outside diam.) is the .30 caliber government round of 1906.
The .45-70 was named in the blackpowder days when a .45-70 cartridge was a .45" bullet with 70 grains of black powder behind it.
Then when smokeless powder was created the .30-30 Winchester was named because it had a .30 caliber bullet with 30 grains of the smokeless powder behind it. Normally though the first number or the only number is either approximately or exactly the outside diameter of the bullet.

Yes, 1mm is about .040 or .03937. Oh yeah and 5.56 NATO is what many call the 5.56x45 cartridge, which is the European method of naming. 5.56mm is the same as .22 caliber, thus the bullet diam and the 45 is the case length in mm, much longer than a .22 cartridge case.

brad cook
 
glnflwrs said:
The 5.56 NATO round is the .224 cal m-16 cartridge.

Actually it's a .223, no big deal, but a little warning the 5.56 nato is loaded a little hotter and not all .223's will handle, check your manual, most will but just check. Rifle rounds can really get confussing. 7mm.08= 7mm (.27 bullit) in a necked down .308 carthridge, Now we have the new short magnums .243 WSM, .270 WSM.. 7mmSTW. .300WSM, plus Weatherby made there own proprietary rounds. I have a friend who has a .375 R.D Jones It is 45.70 Case necked down to a 375 H & H packs a lot of wallop in a pistol, He uses it for Brown Bear in Alaska.
 
haha, i had such a hard time wrapping my mind all around this "caliber" naming stuff. It is really complicated! How i learned is i just bought a coffeetable book that had a bunch of guns, and started reading about them, while making rational conclusions.

took a while... haha
but if you are ever with a gun nut, dont try and shoot the Sh** with him by using "gun lingo" you dont know. it would be like an old guy trying to relate to his son about computers.... "hey son, say, i have about 500 rams of internets.... how many gigatids can i fit on my hardfloppy?"

haha... hardfloppy

slick :D
 
Hey Dig, I was always wondering what the "06" of 30-06 meant, thanks for clearing that up. Basically as was already stated, the common terms used for measuring bullet dimensions are often not their exact dimensions, although they're usually in the same ballpark. Another anomaly is the 8mm kurz (mauser) round which is actually 7.92mm. Also, some bullet sizes can come in all different lengths, eg "7.62mm" could mean 7.62x51mm (7.62NATO), 7.62x39mm (AK), 7.62x54R (Russian), 7.62x63mm, (30-06) etc. To further complicate things, 7.62x51/NATO can also be called .308cal. (If you're buying it commercially, it's probably going to be .308 unless it's military surpluss ammo) I think the point that I'm making is that you just need to know the terminology as the measurements aren't always exact, as was stated by others in the thread.
 
it isnt always clear.... especially when my friend came screaming at me down the range when he found out i was loading my .357mag with his .38 shells.

"DOONT!!!"

haha... it turns out he didnt know that both rounds are actually around .36 inches.

extremely confusing. Especially when trying to explain it to a person who has very limited gun knowledge.

slick
 
Davidoc said:
You can't do it the other way around though, right? (I could be totally off here)

The .357 case is 1.290" in length where the .38 Special uses a 1.155" case so that a .357 Magnum cartridge will not fit into a firearm chambered only for 38 Special. (You should always check your ammo anyway, DO NOT fire a .357 Mag cartridge in a .38 Special even if it will fit. That would be a bad thing.
 
slick519 said:
it isnt always clear.... especially when my friend came screaming at me down the range when he found out i was loading my .357mag with his .38 shells.

"DOONT!!!"

haha... it turns out he didnt know that both rounds are actually around .36 inches.

extremely confusing. Especially when trying to explain it to a person who has very limited gun knowledge.

slick

The .38 and the .357 mag are identical diameters, identical shells, but the caseing is longer on the .357, hence more omph! All .357 revolvers will shoot .38s, it is one of the selling points of the gun, cheaper practice ammo with less kick, same with .44 special and .44 mag. The reverse is not true, guns chambered specifically for .38 have shorter chambers, lighter barrels and thinner cylinder walls and won't be nice to you if you try to shoot the magnums thru them, this is ecspecially true of older revolvers or light weight models. It is real important that you don't just look at bullit diamater and shell size when determining what to put in your gun! Lots of ammo is desighned for specific feeding type wepons, for instance almost all semi-auto pistol ammo won't work in revolvers, because the casing rims are shorter and they'll fall out of the chambers. Case in point, .45 long colt and .45 A.C.P are not interchangeble, although there are some revolvers that will shoot the auto ammo with special clips as an accesscorie. Do not put ammo desighned for revolvers in semis, it will not feed ar eject, not a good thing. Guns are a lot like big Power amps, hooking it up the wrong way can cause pain! CONSULT YOUR OWNERS MANUAL!!!!!