Okay, so there are a lot of ammunition types out there and many more made every year. As a result, it's easy to get over your head with different grains, bullet types, cartridges, calibers, gauges, and primers. This guide is meant to alleviate some of that confusion.

Anatomy of a Cartridge

There is a misconception that the “bullet” is the thing you put in your gun. This is only half true. The cartridge is what you load into gun. The bullet is what comes out of the muzzle when you pull the trigger. A bullet is the projectile that is attached to the front end of a “cartridge”, which is also called a “round”. Inside the cartridge is the gunpowder, which propells the bullet from the chamber. On the back of the cartridge is the primer. Depending on the type of cartridge, this either consists of a light explosive around the rim of the cartridge (hence “rimfire”), or another impact-sensitive explosive nested into the center of the rim (hence “centerfire”). Shown to the right is a cut-away diagram of a centerfire cartridge.


You can think of the caliber as the size of the bullet. More accurately, though, it is the measurement of the bore of a rifle or the diameter of the projectile it fires. Most of the time, American made cartridges are labeled in hundredths or thousandths of an inch. For instance, a .223 rifle round refers to a bullet that is 223/1000ths of an inch wide at its widest point. Most foreign rounds are listed in millimeters, like the 7.62 x 39, the round that the AK-47 shoots. In this case, the first number, “7.62” refers to the diameter of the bullet, and the second number “39” refers to the length of the cartridge in millimeters.

Rifle Ammunition

Rifle rounds hold the greatest diversity in terms of bullet size, caliber, and use. They range from small subsonic .22 rimfire, to the cannon-like .50 BMG. Most are centerfire, but some, like the .22, are rimfire.

The most prevalent calibers of rifle ammo are:

  • .22 LR – This cartridge is used for anything from simple plinking to varmint hunting. The small cartridge is lightweight and is thus easy to carry alot of. It’s also very easy to manage, having very little recoil due to the small amount of powder behind the bullet in the case. It is very fast, however, and can kill small game up to around 150 yards.
  • .223 – This round has been around since just after the Korean War, and is used in the ever popular AR-15 among other rifles. The bullet itself is just a little bigger than a .22 LR, but there is a substantial amount of powder behind this bullet, increasing its range to around 300 yards before accuracy suffers.
  • .308 – The .308 is a very popular cartridge used by the armed forces and hunters alike, because of its stopping power, and range. It’s used for taking large game, such as deer, pronghorn, and the occasional elk or moose.
  • .30-06 Springfeild – This caliber has seen action in almost every war from WWI to the present day. It has the stopping power to kill a bear in a pinch, and is suited for many types of large game. It has been slightly eclipsed by the .308, mainly because it has more recoil, and less velocity. It is more accurate than the .308 at 500 yards however, and is still very popular.
  • .243 Winchester The .243 bullet is slightly bigger than the .223, but it has a much larger cartridge, and can provide more power and range. It is much more accurate than the .223 at 500 yards, but is more expensive.

Handgun Ammunition

Handguns are mostly used for competition shooting and defense, and thus accuracy and stopping power are key. These are some of the most popular handgun rounds on the market today.

  • 9MM – This pistol round is very popular in the military, and also to the self defense world. It is easy to handle, with less recoil than it’s larger counterparts. It is also very easy to find. However, it has less stopping power than desired by many law enforcement and military operatives. It is a good choice for those who don’t feel comfortable with anything bigger, but if you go bigger and shoot accurately, it may be a good idea.
  • .45 ACP – This cartridge has been around since World War I, and was developed for the immortal M1911. It has higher stopping power than most pistol cartridges, and moderate recoil. It’s relatively popular among law enforcement and self defense circles, due to its combination of high accuracy and stopping power, and moderate recoil.
  • .40 S&W – It has been said that the .40 S&W is a more efficient round than the .45 ACP. It has less stopping power, but it has less recoil, and so the shooter can re-aquire his/her target much faster with a .40 than he can with a .45. It is also very popular on the market, and is a favorite among the CCW world.
  • .357 Magnum – The .357 Magnum has an elongated cartridge, and thus holds more powder and shoots harder. In a pistol, it’s used for hunting small game, but is kind of impractical for self-defense. There are rifles chambered in .357 that are useful for hunting deer and the like as well.
  • .380 ACP – This round is used mostly for self defense and is loaded into anything from a pocket pistol to a snub-nosed revolver. It has stopping power, and accuracy, and is a little easier to handle than the .45 ACP.
  • .38 Special – This round has been in use since 1898 and has been used mostly in revolvers. It actually has the same bullet diameter as the .357 Magnum, but the cartridge is .38 inches wide.

Shotgun Ammunition

Shotguns are used for competition, home defense, hunting, and other applications. They have high recoil, but can take down a deer or human without much effort. They are also very easy to shoot, and are very reliable. They typically come various gauges and lengths. The gauge is the width of the shell, and the length is the length of the shell (Duh). The length of the shell determines how much shot and powder can be placed in the shell, whereas the gauge is how large of shot you can fit into the shell. Similar to wire, the higher the gauge, the lower the diameter. For instance, a 3″ 20Ga shell is going to be more powerful than a 3″ .410 gauge, but less powerful then a 3″ 12 Gauge.

You can use two different kinds of projectile in a shotgun shell, a slug (or sabot), and shot. A slug is essentially a stumpy bullet, whereas shot is several small balls crammed into the shell. The size of shot is very important when hunting waterfowl, shooting trap or skeet, or home defense. In general, the higher the number, the smaller the shot, and the more there is in one shell. For example, a No. 8 Dove load will have lots of tiny .09 inch pellets, but a #4 Turkey load will have larger pellets, but fewer in the shotshell. Buckshot works the same way. If I have 00, or “Double Aught”, then there are going to be maybe five pellets in the shell, and they’ll be around .33 inches wide each.

  • 10 Gauge – The most powerful commercially available gauge out there. It’s mostly used for waterfowl hunting, but it kicks like a mule, so it’s kind of useless for home-defense.
  • 12 Gauge – The most available shotgun shell in the US. Vastly popular, it’s used for anything from trap shooting to home defense, to hunting large game like deer.
  • 16 Gauge – Not as readily available as the 12 gauge, the 16 gauge is also powerful, and has a better shot pattern than the 20 gauge, but weighs much the same.
  • 20 Gauge – Easier to handle than the 12 or 16, the 20 gauge is the next most available shotgun shell on the market. It’s also much easier for smaller people to use, which makes it a great first shotgun, and can be an excellent choice for home defense, when you want to stop, but not obliterate your target.
  • .410 gauge – The smallest gauge on this list, the .410 is oddly measured in caliber instead of gauge. If it were, it would be close to 68 gauge. It is very easy to manage, and often is sold in a youth model.

Bullet Types

There are many types of bullets, from the anti-personnel Hollow-Point to the accurate and light Boat-Tail Bullet. Below is a list of bullets and their uses.

  • Frangible (F) – Frangible bullets will disintegrate upon contact with a surface harder than the bullet itself. Frangible bullets are often used by shooters engaging in close quarter combat training to avoid ricochets; targets are placed on steel backing plates that serve to completely fragment the bullet. Frangible bullets are typically made of non-toxic materials, and are frequently used on “green” ranges and outdoor ranges where lead abatement is a concern.
  • Full Metal Jacket (FMJ) – These are generic bullets, found on most rifle and pistol cartridges. They are more streamlined than Hollow Points, and provide more penetration.
  • Hollow Point – These bullets are Hollow have the top scooped out, which allows them to expand upon impact, delivering more force and internal damage. Due to this fact, militaries are banned from using this “overly lethal” round. However, it is quite popular with self-defense and law enforcement. Many hunters use it as well, since the bullet loses a good deal of velocity upon impact, and thus reduces the risk of hitting something behind the target.
  • Round NoseAlmost exclusively found on pistol rounds (except the 22 LR), this round is similar to the FMJ, except it is less aerodynamic.
  • Soft PointThese Bullets are like the Hollow Point, except they don’t expand as much. Their soft core is slightly exposed, making the bullet less penetrating.


Federal law requires that you must be at least 18 years old to purchase shotgun ammunition and 21 years or older to purchase handgun and rifle ammunition.