Firearms question

[icedoverfire]

Hi gents,

I don't own any firearms, nor do I have any real need to own one but I'm curious: When someone is referring to ammunition, what does each number mean?

Specifically, take 5.56x45mm NATO ammunition... What is the 5.56 referring to and what is the 45 referring to?

I understand the colloquial "bullet" is really only the slug that is fired from the barrel of the gun and the casing is what is left behind... the whole assemblage is the cartridge.

Thanks,

-ice

 

[Phog Allen]

Hi Ice. The nomenclature you refer to is the calibre and length of hte ammuntion. In this case, 5.56 refers to the diameter of the projectile in millimetres. In America we use a fractional system and of course 5.56 refers to metric. There are standards most manufacturers have agreed to such as nominal bore sizes. 5.56mm is a NATO round standard that translates to .224 diameter. There have been a few other 22s over the years with varying diameters from .221-.229 but .224 is the current western democracy "standard". The Ruskies use a slightly larger(I think) diameter .22. The 45 refers to the length of the cartridge in millmetres. Hence, 45mm.Most European rounds are designated with metric measaurements. A very famous one was Peter Paul Mauser's 8X57. 8mm bore diametre, 57mm case length.

There are other acrcaic measurements in ammo as well. You will see a lot of refernce to "grains" of powder or bullet weight. 1 American pound = 7000 grains. Bullet weight and powder is usually the only thing weighed in these amounts. It leads to much greater measuring accuracy with the smaller units. It has been around a long time.

And yet another measure you will see is drams. It is associated these days exclusively with shotgun shells or possibly period accurate muzzle loader charges. You will see shotshells with the momentclature "2-1/2 Dram Equivalent" or similar. This is a holdover from blackpowder days when charges of blackpowder were measured in drams weight.

Yet another nomenclature you will see is somethign like "45-70" This refers to the calibre of the projectile in inches followed by the charge of powder in grains. Again, a holdover moslty from the blackpowder days. Most cartridges named after the smokeless powder revolution will have a calibre designation in either millmetres or inches followed by the year, name of company or designer who developed it, or something catchy like "Hornet" or Swift" or "Magnum". The firearms industry is even more traditional than wet shaving and you can spend a lifetime learning it. It is also quite a lot of fun.

Regards, Todd

 

[Phog Allen]

I thought I might add that if you really want to thoroughly confuse yourself start trying to deicpher British ammunition designations from the nineteenth and early twentieth centurys. Take the 47-70 designation. In some of the old Nitro rounds of professional hunter fame, something like .500-450 Nitro Express, they are giving you the calibre first like the .45-70 but instead of powder charge you are usually getting the bullet weight in grains. So you can see there has been much confusion in the arms world. Much of it stems from the smokeless revolutioln of the late nineteenth century. Firearms really hit a zenith in that era the changes came rapidly. It caused a lot of renamng and of course confusion. Nitro rounds aren't hard to decipher but wait till you try to keep up with the "mark" system they used for martial ammunition!

Regards, Todd

http://en.wikipedia.org/wiki/Nitro_Express

 

[Mazeman]

Who's going to tell him the .38 and the .357 actually have the same diameter (.357 inches)?

Let's just say the nomenclature is a bit crazy, and experience helps sort it out.

For instance, the .223 and the 5.56 round have the same diameter, yet due to slightly different configurations of the cartridge the .223 can be fired from 5.56 rifles, but the 5.56 cannot be fired from all .223 rifles.

 

[RHVette]

Don't forget rounds like .30-06 Springfield which is actually an abbreviation of .30 calibre, adopted 1906. And then there's always the multiple names: 9mm Kurtz, 9mm Browning Short, .380 ACP, etc., etc. Oh, and last but not least, the ones that are wrong. .38 and .357 is one, another is 9x18 Makarov, which is actually 9.2 mm diameter.

 

[soapbox]

Who's going to tell him the .38 and the .357 actually have the same diameter (.357 inches)?

Let's just say the nomenclature is a bit crazy, and experience helps sort it out.

For instance, the .223 and the 5.56 round have the same diameter, yet due to slightly different configurations of the cartridge the .223 can be fired from 5.56 rifles, but the 5.56 cannot be fired from all .223 rifles.

...And the 5.56 has a different primer configuration, making it a pain to reload empty brass shell casings into ammunition.

The rabbit hole can go pretty deep!

 

[RHVette]

...And the 5.56 has a different primer configuration, making it a pain to reload empty brass shell casings into ammunition.

The rabbit hole can go pretty deep!

Well, that's just because it has a crimped primer pocket to function in M249s, isn't it? I've never had a problem reloading 5.56 if I swage the brass first.

 

[soapbox]

Well, that's just because it has a crimped primer pocket to function in M249s, isn't it? I've never had a problem reloading 5.56 if I swage the brass first.

I think so--I just don't have a swager press for undoing the crimps. (Well, I don't have a .223/5.56 rifle right now either...)

 

[Phog Allen]

Well if we are going to go this route, lets tell him about the .44 Magnum handgun round that is actually .429 calibre rather than .44. Or maybe the .480 Ruger that is actually .475 diameter.

Regards, Todd

 

[Teh Chooch]

So, the moral of this story is: The numbers are measurements, be it metric or standard typically, but each caliber should be researched individually, as most of them have a unique story behind the actual dimensions. "Fifty Cal" usually means about .5" in diameter, but there is a HUGE difference between say, .50BMG and .50AE

If you ever get into reloading, you'll find out that the advertised caliber doesn't always add up to the actual cartridge dimensions.

For example the cartridge on the far left is .50 BMG and the 5th Cartridge from the left is .50AE. The diameter is pretty much the same, but as you can see the amount of powder that can be jammed in the casing, and the amount of mass in the bullet are pretty different, even though the names are almost the same.

(Watch out for that when buying .357 mag ammo, and the guy behind the counter at wally world hands you .357 Sig!!)