There are so many different kinds of ammunition available for rifles, pistols and shotguns that it can be hard to know where to start. What's the difference between ball and soft-point rounds? Do you need high-brass or low-brass shotgun shells?

In this guide, we'll introduce and explain the basic characteristics of the most common types of ammunition. Note that terms, measurements, and color codes are not always consistent across all manufacturers; the standards you'll see here are the most common, but there are others.

Rifle and Pistol Round Anatomy

For the most part, rifle and pistol rounds have the same basic anatomy consisting of five parts. The entire unit is referred to as a round or cartridge.

• The case is the brass or steel body that contains all of the other components.

• The bullet is the solid metal projectile fitted into one end of the case.

• The rim is the crimped end of the case, shaped such that the firearm's extractor can grab and eject the empty casing.

• Inside the case is the gunpowder that propels the bullet out of the barrel.

• The primer is the part of the round struck by the firing pin, which creates a spark sufficient to ignite the gunpowder.

Choosing Rifle and Pistol Rounds

There are hundreds of different rifle and pistol rounds, but a small fraction of them comprise the majority of rounds sold and fired. The four primary considerations in choosing a round are caliber, load, grain and type.

• Caliber describes the physical dimensions of a bullet and is measured in either inches or millimeters.

• Load refers to the amount and type of gunpowder in the casing.

• Grain refers to the mass of the bullet itself (not to the type or amount of gunpowder, as is commonly believed).

• Type categorizes rounds by intended purpose.

Caliber

In general, as bullet size increases, so do price, recoil, effective range and stopping power, while magazine capacity and effective rate of fire decrease.

Load

Gunpowder is a complex topic, but fortunately, it usually doesn't make a big difference to the everyday shooter. Unusual or custom blends of gunpowder are generally employed only by competitive shooters and advanced hobbyists. When shopping for target or self-defense rounds, you'll want to pay more attention to caliber, grain, and type.

Grain

A bullet's grain is a simple measurement of its mass. A "grain" is a unit of weight equal to 2/875 of an ounce — so when you buy a box of 55-grain .223 rounds, each bullet (not the round, just the bullet itself) weighs 55 grains, or roughly 0.126 ounces. A bullet's weight has significant effects on its speed, stopping power and penetration, with heavier bullets generally hitting harder and penetrating, expanding or fragmenting more significantly.

Type

You'll also need to carefully consider the type of bullet, especially if you're shopping for defense rounds. Many (but not all) bullet types come in both rifle and pistol variants.

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  Blanks
  Blanks are gunpowder-filled casings that don't contain a bullet at all, mostly used for training or special effects purposes. Even though there's no bullet, blanks still discharge small fragments of metal at high speeds and can injure or even kill people or animals at close range.

• 

  Full-Metal and Total Metal Jacket
  Ball or full-metal jacket (FMJ) ammunition is typically the simplest and cheapest type. The bullet is a solid, conical piece of metal that doesn't fragment on impact. It has poor to average performance against armor but overpenetration is likely with soft targets (although these factors are also heavily dependent on caliber).

  Complete and total metal jacket (CMJ/TMJ) rounds are almost the same thing as FMJ rounds. The differences are subtle and generally have no impact on ballistic performance outside of very specific situations.

• 

  Hollow-Point
  Hollow-point rounds are designed to expand on impact while still remaining in one piece, dramatically increasing the bullet's surface area, and therefore the damage it can cause to soft tissue in exchange for minimal penetration.

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  Soft-Point
  A soft-point bullet strikes a nice balance between FMJ and hollow-point rounds in terms of penetration and expansion. Whereas FMJ rounds have hard, copper shells, soft-point rounds have some exposed, soft lead at the tip of an otherwise closed shell. This means that the bullet will expand on impact but isn't likely to do so as much as a hollow-point would.

• 

  Frangible
  Frangible bullets have scored tips or are otherwise designed to fragment into many small pieces on impact. Ballistically and tactically, they are essentially the opposite of FMJ rounds. Penetration is minimal, and the many small fragments create multiple wound channels, increasing stopping power.

• 

  Wadcutter
  Wadcutter rounds and their many sub-types are flat-nosed bullets generally used for shooting at paper targets. The flat nose dramatically increases drag and thus reduces the bullet's velocity, but some people use them as defense rounds, particularly in short-barreled firearms where the bullet's maximum velocity is limited by the barrel's length anyway.

Color Codes

In many cases, rifle and pistol rounds have color-coded tips to indicate that the round is designed for a specific purpose. Note, though, that these color codes are not universal. The colors presented here are generally consistent across military vendors but may differ elsewhere.

• Ball/FMJ rounds have no color.

• Armor-piercing rounds have black or green tips, although armor-piercing 5.7mm rounds have blue tips. Armor-piercing rounds are typically illegal for civilians to own.

• Incendiary rounds contain explosive compounds designed to ignite fuel or dry brush. Like armor-piercing rounds, they are generally illegal for civilians to own.

• Tracer rounds have red or orange tips and leave visible trails in the air, useful for visualizing a shot's path and impact point.

• Frangible rounds, if they are color-coded at all, often have green tips atop a white ring.

Shotgun Round Anatomy

Shotgun shells are, of course, different from rifle and pistol rounds in several significant ways. Their parts are, however, roughly analogous.

• The case is the "body" of the shell that contains all of its other components.

• The shot consists of anywhere from four to twenty or more spherical projectiles made of lead or steel.

• The neck is equivalent to the rim of a rifle or pistol case. It surrounds the primer and is also the part "grabbed" by the extractor in order to both load and eject the shell.

• Inside the case is the gunpowder that propels the shot out of the barrel.

• The wad is a tightly packed disc of cloth or plastic used to separate the shot from the powder, and to ensure that the propellant gases affect each pellet more or less equally.

• The crimp is the folded plastic end of the shell opposite the primer which contains the shot until the shell is fired.

Choosing Shotgun Rounds

As with pistol and rifle rounds, choosing shotgun shells appropriate to your needs requires some basic knowledge — in this case, gauges, loads and brass height.

A shotgun's gauge is analogous to a pistol or rifle caliber, with lower numbers indicating a larger-diameter shell and thus more room for more (or else larger) shot. The most common shotgun gauges are 20, 12, and 10.

There are many different types of shotgun loads, each with a different purpose.

• Field, small game, or target loads consist of many, very small pellets and are generally used for target practice or for birds, rabbits, and the like.

• Buckshot consists of fewer, larger pellets and is used for hunting large game or for personal defense.

• Slugs are single, solid, metal projectiles that replace shot entirely. They are devastating to soft tissue and can penetrate multiple targets easily, especially in larger gauges.

• Flechette rounds fire dozens of small, steel darts as opposed to spherical pellets. These darts fly farther and more accurately than shot but typically have somewhat less overall stopping power.

• Beanbag rounds are small, less-lethal projectiles designed for riot control.

Shotgun shells are either high-brass or low-brass, both of which refer to the height of the neck. Most shotguns will accept either type, but some cycle poorly (or not at all) with low-brass ammunition, in particular.

Color Codes

Contrary to popular belief, shotgun shells do not have any official color-coding system, as rifles and pistols do. Shells may be red, green, black, blue, white or any other color, but the color's significance (if any) depends on the manufacturer.

Shopping for ammunition can feel overwhelming, and there are far more kinds than any single article can cover, but hopefully, you can now choose the right ammo with more confidence. To keep your shooting knowledge sharp, be sure to read about gun cleaning and maintenance basics and the four rules of gun safety.