Thoughts on the calibers that Dan has shot...

Dan's collection of shell casings, representing the calibers he's shot

First, let's define some terms, o.k.? (Note that these definitions are specific to firearms...)


  • Bullet: the projectile propelled by a firearm, i.e., the piece of lead that hits the target.

  • Cartridge: the complete assembly, as loaded into a firearm: the shell, or casing, containing the primer, gunpowder, and bullet.

  • Round: (noun) another name for a cartridge, often used when discussing numbers of cartridges, as in "I just bought 50 rounds of 9mm," or "I've shot over 5,000 rounds through this pistol."

  • Shell: (Definition A) (for handguns and rifles) the metal casing portion of a cartridge.

  • Shell: (Definition B) (for shotguns) the name for the entire cartridge, including the metal and plastic casing, primer, gunpowder, and shot, ready to be fired from a shotgun.

  • Shot: (noun) the small pellets fired from a shotgun.

Got it?


Now, where were we?

Modern pistol and rifle cartridges follow a couple of common naming conventions for their sizes:

  • English and American designations for cartridges are based on inches, and the measurement is typically of the bullet diameter. This measurement is expressed as "caliber." So, for example, a cartridge with a bullet diameter of 0.22 inch is called .22 caliber. It's pronounced without the decimal, so you would just say "twenty-two caliber."

  • Metric designations for cartridges are expressed in millimeters. Thus, a cartridge with a bullet diameter of 9mm is simply called "nine millimeter."
So far so good - however...

There are so many different kinds of cartridges that it's not enough to just say the diameter. For example, I know of 7 varieties of .22 caliber cartridges! So, there are two basic ways to distinguish them from each other:

  • a unique name

  • cartridge length

The unique name may be the person or company that developed it (Winchester, Remington, Colt, Ruger) or a characteristic (Short, Long, Automatic, Magnum) or the amount of powder used in it (a .30-40 originally used 40 grains of powder), or even a year (like the .30-06, "thirty aught six," adopted by the U.S. Army in 1906).

Some are referred to by acronyms:

  • ACP: Automatic Colt Pistol
  • S&W: Smith & Wesson
  • NATO: North Atlantic Treaty Organization

The cartridge length is usually used for metric cartridges, for example 9x19mm ("nine by nineteen millimeter"), which has a length of 19mm.

Are you confused yet? If not, how about this?

Shotguns designations are expressed as "gauge." The gauge of a shotgun refers to how many lead spheres the diameter of the bore (the inside of the barrel) would equal a pound. In the case of a 12-gauge shotgun, it would take twelve spheres the size of the shotgun's bore to equal a pound. (Why is it done this way? I think it goes back to the old cannon days, when a cannon was rated by the size of its cannonball...)

So, a 12-gauge shotgun shell (cartridge) has a diameter of .729 inch, and a 20-gauge has a diameter of .615 inch.

The Photo

So, with all that, here are the names of all the cartridges represented by the empty shell casings in the photo (shown here again for convenience).

From left to right:

Name Info
.22 Short These are small rimfire cartridges, and they're not real common anymore – the last time I shot one was with my Dad when I was 12 years old...
.22 Long Rifle Even though it's called "Long Rifle," it's a very popular round for handguns. I shoot these in my Ruger Mark III pistol. Also a rimfire cartridge.
.25 ACP A very small, low power cartridge, used mostly in pocketable pistols for short-range self-protection. These – and all the others from here on – are centerfire cartridges.
.380 ACP The 3-digit size number (.380) helps to distinguish it from other .38 caliber rounds. Gaye and I shot these from a friend's pink Taurus 738 TCP!
9mm Luger Also known as 9x19mm. This is what I shoot in my Hi-Point carbine. I also shot them for years in the Air Force, from a Beretta M9 pistol, and qualified "Expert" every time.
.38 Short Colt Nearly obsolete, it's what fits our old WWII revolver. No guns are made in this size anymore, but a couple of companies make ammo for use in vintage guns. This one is a Remington.
.38 S&W Special Introduced in 1898, this is one of the most famous, and most popular, revolver rounds ever. I qualified "Expert" with a .38 Special revolver as part of my Air Force training in 1982.
.357 S&W Magnum Interesting trivia - I shot this .357 Magnum, and the .38 Special next to it in the photo, from the same gun! How? They both have a bullet that's 0.357" diameter, and an outer casing dimension of 0.38".
.40 S&W This is becoming popular as a handgun round, but I've only shot it once, from a friend's Beretta 96 pistol.
.44 Remington Magnum Note how long the Magnum cases are – this .44 is similar in diameter to the .45 ACP, but it definitely kicks a lot more. Gaye, Allen, and I have all had fun shooting .44 Magnums from a very large Ruger revolver!
.45 ACP This particular steel casing in the photo is meaningful to me – Allen and I shot it at a shooting range that rented us a fully automatic .45 caliber WWII Thompson submachine gun (Tommy gun)!
.223 Remington Now we get into rifle cartridges: the .223 is about the same bullet diameter as the little .22's on the left, but with a LOT more powder behind it. I shot these from a friend's AR-15 rifle (a semi-automatic, civilian version of the M-16).
7.62x39mm Also called 7.62mm Soviet. This is what the AK-47 uses, but I shot it from an SKS rifle (an older Russian battle rifle).
7.62x54Rmm The same diameter as the 7.62 Soviet, but with a substantially longer case. Introduced in 1891, it's still in military use today! We shoot these in our Mosin Nagant rifle. (It's a full cartridge in the photo because I didn't have an empty one.)
20-gauge I shot this from a Remington shotgun on an outing with Allen's Boy Scout troop. It was loaded with No. 9 birdshot (0.080" diameter each)
12-gauge Gaye and I have shot a couple of 12-gauge shotguns (ouch!). This particular shell was loaded with No. 4 shot (0.130" diameter each).

Hey, thanks for reading this far...I really appreciate it! Plus, you never know when we'll be adding to our collection...Dan has now also shot a .30-30 and a .22 Magnum...

See our list of quotations about firearms and shooting by clicking here!