Ammunition is important. Without it, your firearm is basically a fancy hammer. But for people who are new to guns, the topic of ammo can be a confusing land of terms and numbers. Even for people who have been shooting awhile—if you’ve never been the one to buy the ammo, a trip to your local store might have you overwhelmed with all the choices you didn’t even realize you had.
Let’s dig into a few of the basic terms and numbers commonly found on a box of ammunition so you can be prepared to find what you need.
“Bullet”
Actually, you’re not going to see bullet on a box of ammunition. Bullet refers to a metal projectile that comes out of a gun. And while many people may use the word to refer to any ammo they put into a gun, the bullet is actually just part of a cartridge. To make things even more confusing—a bullet has nothing to do with a shotgun shell.
So now you know. When you head to the store for ammo, you’re actually buying cartridges or “rounds” or shells—not bullets.
Cartridge/Round/Shell
What’s the difference? Cartridges (often referred to as “rounds”) go in rifles, pistols, or revolvers. Shells go in shotguns.
If you really want to dig into it, one single cartridge is made up of the casing, primer, powder, and a projectile all assembled and ready for use. When fired from a gun, it sends one thing down range—the projectile, or bullet.
Notice in the picture below—the darker copper colored piece that sits at the top of all those cartridges is the actual bullet. That’s what comes out the muzzle of your gun and goes down range.
By contrast, one single shotgun shell is made of the hull/case, primer, powder, wad, and pellets, all assembled and ready for use. When fired from a gun, it sends many smaller pellets down range—all the pellets, or “shot”.
In the picture below, all the pellets are inside the red and yellow shells.
It’s worth mentioning that you can also purchase slugs for shotguns, which is a shell containing one bigger metal projectile instead of several smaller pellets. Slugs are used in situations where you want a bigger projectile, but can’t, for any number of reasons, use a rifle. (The slug is lying on its side in the picture above and if you look carefully you can see the size of the projectile inside— from the white end of the shell to the “o” of Rottweil.)
Why does it matter? Cartridges and shells are intended for use in guns that serve different purposes. Generally speaking, rifles and handguns are meant for shooting stationary targets (therefore, one projectile). Shotguns are generally intended for moving targets (therefore, a spray of shot and a better chance of hitting the moving target).
Caliber/gauge
You need to buy ammo that is made to fit your gun. Without getting too far into the differences in calibers (rifles/handguns) and gauges (shotguns), I’ll simply point out here that a 9mm, a .45, a .223, and a 10 gauge all take completely different ammunition.
A question I’m often asked by beginners—for instance, a friend out shopping for her first box of ammo to bring home with her new handgun— is does certain 9mm ammo go in certain 9mm guns.
No. In most cases, a 9mm firearm will take any 9mm ammo. If you have a 9mm, it doesn’t matter what box of ammo you choose, those rounds will technically work in your gun. While you may get better performance from certain brands of ammo, or want to choose a certain grain, casing, point, etc, for your purposes, 9mm is 9mm is 9mm—and all of them will fit in and can fly downrange from your gun.
Grains
When shopping for cartridges, you may notice there are different numbers of “grains”—sometimes abbreviated as Gr. Many people think this has something to do with the amount of powder in the casing. As in, the higher the number of grains, the more power the bullet has behind it.
Negative, ghost rider.
Grain is actually a measurement of weight, and grains are used to say how large the projectile (bullet) of the cartridge is. Grains are super small — 437.5 grains = 1 ounce. Another way to look at it is 1 gram (think of a stick of gum, a dollar bill, or a paper clip) is the same as 15.43 grains.
So if the box of ammo you just bought says 9mm 115 GR. FMJ, it means that the actual bullet that flies down range weighs 115 grains (or, if my math is correct, about 7.45 grams).
I’m not sure why they don’t just go by grams. Maybe it’s an unnecessarily complicated gun thing.
Why do grains matter? So you can match up the projectile with your purpose in shooting. For instance, 115 grain 9mm is plenty for target shooting at the range. Lighter bullets shoot faster and flatter than heavy bullets. Self-defense rounds have a heavier grain—the bigger and tougher the target/game, the heavier your bullet should be. Heavy means more energy and deeper penetration, right?
You can go into gun forums and hear many arguments for and against using a lighter or heavier grain in various situations. There’s always something to have an opinion about when it comes to ammunition.
Or, you know. Guns.
Birdshot/buckshot/number x shot/target load/game load
When purchasing shotgun shells, you will notice a number on them referring to “shot”. Perhaps you’ve heard people talk about birdshot or buckshot.
Birdshot is referred to as, for instance, a “number 2 shot” or an “8 shot.” The number 2 shot contains far less pellets per ounce than a number 8 shot. Different numbers of shot are used for hunting different game.
Buckshot is similar to birdshot in that there are many pellets inside of the shell, but buckshot is made of significantly larger pellets. So, less pellets than birdshot, but each pellet in buckshot is much larger than birdshot. Buckshot still scatters outward when it is fired, but because the pellets themselves are much larger they cause significantly more damage than birdshot. Buckshot is generally used for larger animals or home defense. Using buckshot to hunt a duck or a rabbit would be pointless—there would be nothing left of the animal.
Target load and game load (and other kinds of loads) clue you in to what the ammunition is best used for. Hunting certain game or shooting clay pigeons, for example.
Centerfire/Rimfire:
These terms refer to where the firing pin hits the cartridge to ignite the primer when the trigger is pulled. Centerfire hits the center of the cartridge, rimfire hits the rim of the cartridge, as shown in the picture below. Centerfire is generally found in larger caliber ammo and is said to be more accurate with less chance of misfire/malfunction.
Brass/Steel/Aluminum casing (handgun/rifle)
Any responsible shooter knows that when you’re done shooting, you should pick up your brass (unless you’re at a range that does it for you). This refers to cleaning up all the brass casings that have been ejected from your gun after all that practice you just did. Not only is it the nice thing to do, it’s also essential for shooters who reload their own ammo. (They reuse the casings.)
But not all handgun/rifle round casings are made of brass. You can also get steel casings or aluminum casings. Steel and aluminum casings are cheaper, but some shooters argue that they are harder on your gun. It has been said that brass casings are “cleaner” for your gun and result in fewer malfunctions.
Note: Shotgun shells are not included here as they are made of plastic. But you should still be awesome and clean up whatever your gun is ejecting wherever you are shooting, whether it’s a metal casing or a plastic hull.
Duh. Be responsible, fellow shooters.
Roundnose/Bullnose/Hollowpoint
The tip of the cartridge will generally be rounded or have a hollow point. Rounded ammo is intended for plinking, target shooting, and some hunting. Hollow point is intended for hunting or self defense. Hollow point ammo expands differently to cause more damage to its intended target.
Ammunition basics: there is a lot to keep straight
As ammunition gets more specific to different shooters’ needs, there will always be more terms to learn. We could spend entire articles talking about one specific kind of shell or cartridge! But hopefully these basics will point you in the right direction when you’re standing among the many choices of boxes to buy.