What are the Basic Parts of Ammunition?

What are the Basic Parts of Ammunition?


Bullets, ammo, rounds, cartridges, ammunition…there is a lot of terminology used to describe ammunition. To the uninitiated it can be confusing. In this blog we want to offer a clear explanation of the basic parts of ammunition, and maybe clear up some of the confusion around the different terminology used to describe it. Below, we’ll dive into the basic terminology, so keep reading!

Basic Terminology

Let’s begin with some basics, defining some words you’ve doubtlessly heard on the range. It’s important that we begin on the same page, in order for the rest of this article to make any sense. Here they are, offered here in no particular order:

  • Ammunition: the collective term for the complete, assembled cartridges fired by a given firearm. This is frequently shortened to “ammo.”
  • Cartridge: a single unit of ammunition, consisting of everything needed to fire one shot, except the gun. A cartridge consists, at a minimum, of a primer, case, propellant, and projectile. We will discuss each of these elements in much more depth in this article.
  • Bullet: the projectile fired by most guns, excluding shotguns. This is sometimes erroneously used to describe the entire cartridge.
  • Round: Another term for a single cartridge, frequently used as, “load six rounds in your magazine,” or “make sure there isn’t a round in the chamber.”
  • Shotshell: a single round of shotgun ammo; not a true cartridge.

With that out of the way, let’s take a look at each component of a cartridge. There are four major components that combined, create a complete cartridge. They are the cartridge case, primer, propellant, and projectile.

The Cartridge Case 

We will begin with the case because it is the most visible part of the cartridge and it acts as the structure for the cartridge. The case gives the cartridge its shape and performs a lot of other really valuable functions.

Cartridge cases are typically made of brass, but may also be made of other materials including steel and aluminum. Most cases are plain, uncoated brass. Aluminum cases are usually a dull silver, and steel-case ammo is green or grey. Sometimes ammo, especially premium hunting or defensive ammo, is nickel-plated and has a shiny, silvery appearance. Starting at the base is the head of the case. Viewed from the rear this offers some information in the form of a headstamp. The headstamp usually includes the manufacturer and caliber of the ammunition in question, and sometimes (especially with military ammo) other symbols or codes.

The head of the case also provides a means for it to be extracted from the firing chamber. In some cartridges, especially revolver cartridges like .38 Special or .357 Magnum, this is a raised rim. In the case of modern semi-automatic pistol cartridges and rifle rounds, this rim will be no wider than the case itself. Instead, there is a groove around the head of the cartridge to provide a place for the extractor to grab it and remove it from the chamber.

The body of the case varies drastically depending on the cartridge. Some, especially revolver cartridges, are straight walled from base to neck. Others are angulated, having a shoulder, a narrower neck, and a mouth into the which powder is poured and the bullet is secured. These are known as bottleneck cartridges. The case provides volume for the storage of gunpowder and protects it from exposure to the elements.

The cartridge case is also responsible for head spacing. Headspace is the depth into the firing chamber in which the cartridge is inserted. A cartridge that is allowed to fall too far forward into the chamber can cause serious problems. In a revolver this could case mechanical lockup by putting the bullets so far forward in the cylinder that they come of the other end and prevent the cylinder’s rotation. In a high-powered rifle a cartridge too deep in the chamber can cause pressures that greatly exceed safe limits, potentially damaging your gun and harming the shooter. In the case of rimmed cartridges, the rim controls the headspace. In most (but not all) rimless cartridges, headspace is controlled by the mouth of the cartridge resting on a ledge in the chamber.

One particular class of cartridges known as “belted magnums” have a raised rim (the belt) just above the extractor groove. These cartridges are generally limited to very powerful, magnum rifle cartridges like the .300 Winchester Magnum and .375 H&H Magnum. The belt headspaces the cartridge by coming to rest against a ledge at the rear of the chamber.

In the case of a shotgun shell, most of the case is usually plastic. The base, which includes a rim and a headstamp, as well as a primer pocket (see next section) is usually made of brass. The plastic section holds the projectile(s), which are usually enclosed, unlike most rifle and pistol ammunition.

The cartridge case performs a lot of functions. It is the structure for the cartridge. It holds all the other elements in place and protects them. The case has a provision to allow itself to be extracted from the chamber, and it is responsible for controlling headspace. Let’s move on to the primer.


The primer is located at the rear of each cartridge and shotshell. It is a small cup containing priming compound. It fits into a place in the case known as the primer pocket. In most cartridges and all shotshells it is located in the center of the rearmost portion of the case. These are known as centerfire cartridges. The priming compound is an explosive chemical compound that ignites when the primer is struck with significant force, in this case the firing pin. When the firing pin strikes the primer, it sends a jet of hot flames through the flash hole and into the gunpowder, firing the round.

There are two categories of primers for centerfire ammunition. Berdan and Boxer. Berdan primers are common in centerfire cartridges manufactured in the United States. They are known as “non-corrosive” primers. Boxer-primed cartridges are fairly uncommon. However, it is important to recognize them because they contain a corrosive compound. If not cleaned immediately after firing they can harm your firearm.

One notable exception to the center placement of the primer is with rimfire ammunition. Rimfire cartridges such as the .22 Short, Long, Long Rifle, .22 Winchester Magnum Rimfire, and the .17 Hornady Magnum Rimfire, are referred to as rimfire ammunition. The rim of these cases is actually a thin, double wall with a void in between. This void is filled with a priming compound, and the firing pin strikes the rim rather than the center of the cartridge. This is a really antiquated form of priming, but the rimfire ammunition has been around so long that it is embedded. If you’ve ever shot a .22, you’ve shot a rimfire cartridge.

Propellant (Powder)

Between the primer and the bullet, the case contains propellant, or gunpowder. Propellant is ignited by the primer. Although it sounds like an explosion, the powder is actually burning at a very, very high rate. This creates rapidly expanding gas, which creates pressure. The pressure propels the bullet down the barrel and toward its intended target.

Modern propellants are extremely refined. They can be slow-burning or fast-burning. Fast-burning powders are designed to expend all their energy in shorter barrels. Slow-burning powders burn more slowly and perform better in longer barrels. This can help achieve the greatest possible effectiveness depending on barrel length. Modern gunpowder can also have flash retardants that help prevent blinding muzzle flashes when fired at night. They can be optimized for use in rifles, pistols, or shotguns.

Modern small arms ammunition contains gunpowder known as smokeless powder. Smokeless powder, as the name implies, generates very little smoke and dirty residue. Older “black powder” was known for creating prodigious clouds of smoke and being filthy (and corrosive) after just a few shots. With modern, smokeless powder you can shoot hundreds of rounds without accumulating significant grim on your gun. If you ever shoot a black powder gun (or see one shot) you will instantly understand why today’s powder is known as “smokeless”.


Finally, we come to the business end of the cartridge, the projectile. This is usually known as a bullet in the case of rifle and pistol ammunition, and is the portion of the cartridge that is fired downrange.

Bullets are generally described by their caliber and weight. Caliber is expressed either in a standard/imperial measurement like .308 (308/1000ths of an inch) or a metric measurement like 9 millimeter. This will correspond with the internal diameter of the barrel through which the bullet is fired. The next measurement, weight, is give in grains. For example, common .357 Magnum bullet weights are 110, 125, and 158 grains. One ounce is equivalent to 437.5 grains.

Bullets come in a variety of shapes and styles. Though some bullets, often those fired from revolvers, are uncoated load, most bullets consist of a jacket made of a copper jacket and an inner lead core. Bullets may have a Full Metal Jacket (FMJ), or have no exposed lead. These are often the least expensive bullets, and cheap practice ammo is usually loaded with FMJs. Bullets, especially rifle bullets, may have a Soft Point (SP) of exposed lead. This helps the bullet flatten out and expand on target, which helps hunters make ethical, clean kills faster. Bullets may also be of the Jacketed Hollow Point (JHP) variety. These are common for pistol bullets used by police and Citizens interested in self-defense. They expand, dumping maximum energy into the target, and preventing the bullet from exiting and posing a threat to innocents. There are literally dozens of other bullet styles out there, but those are among the most common.

Shotshells usually contain multiple projectiles known as “shot”. Shot comes in various sizes from #9 shot consisting of tiny pellets and suitable for use against very light birds like doves to 00 buckshot, which contains nine, .33-caliber pellets and is suitable for big game hunting and self-defense. Shotguns sometimes fire a single projectile known as a “slug,” a massive .73-caliber projectile weighting a full ounce. Due to this extreme variation is important to choose shotgun ammo according to its purpose.

Regardless of whether it is shooting thousands of tiny pellets or one massive slug, a shotgun shell will also contain “wadding,” a buffer material to separate the shot from the burning powder. The wadding generally falls away from the shot within a few meters of the muzzle when fired.

Trust Grizzly Cartridge for All Your Ammunition Needs

The combination of a cartridge case, primer, gunpowder, and projectile make up a complete round of ammunition. Now that you understand more about the basic parts of ammunition, you can shop with a more critical eye. Different components optimize modern cartridges for different purposes. Understanding ammunition components helps make choosing the right ammo much easier.

Regardless of whether you need rifle cartridges, or pistol rounds, or range ammo, Grizzly Cartridge uses the finest primers, cartridge cases, propellants, and projectiles anywhere. From .223 Remington to 500 Nitro Express, .380 ACP to .500 Linebaugh, for hunting, shooting, or self-defense, we have the centerfire ammunition you need.

Grizzly Cartridges are built from the highest quality components to give the ultimate performance, each and every time. Consistent, reliable, and made-in-the-USA, trust Grizzly Cartridge for your handgun and rifle ammo, regardless of the purpose.