What Are the Basic Parts of Ammunition?


Let us help you learn about one of the foundations of shooting – the basic parts of ammunition. Without it, your firearm is nothing more than a giant paperweight. In the following paragraphs, we will discuss what ammunition is, dispel some of the misinformation surround it, and even give you some basic knowledge related to ammunition and commonly associated terms. So, what are the basic parts of ammunition?

At first glance, the world of guns and ammunition can seem like a lot to take in. This is especially true when it comes to terminology.

Have you ever been corrected, or heard it happen to someone else, after referring to a magazine as a clip, or a semi-automatic rifle called an assault weapon? Next time you visit the local gun store walk up to the counter and ask what bullets would be best for deer hunting and see what happens. Chances are your answer will include a strange combination of stares, wide eyes, and even some outright hostility.

If you are going to participate in any activity it is important to learn the proper terminology (i.e. the basic parts of ammunition), doing so allows you to be understood by other members of the community and even taken more seriously.

Shooting is no different.

Whether you are protecting your home, hitting targets, or hunting it is important to know and apply terminology correctly.

Today, we’ll break down the different components of ammunition so that next time you are at the gun shop buying supplies, or at the range discussing your progress, others know what you are talking about and do not look at you like you are describing an alien landing.

Whether it is a result of poorly written Hollywood scripts, unknowing television news reporters, or simple misunderstanding there is no escaping the fact that when it comes to firearms many people use incorrect terminology.

This often leads to individuals using the correct terminology to describe something wrongly or interchange it. One of the most common mistakes occurs when describing ammunition; which is often referred to as bullets, shells, or brass.

Making this common mistake is a red flag that tells those invested in shooting and guns that there is a lack of understanding or the possibility you have ever shot a firearm.

Of course, firearm terminology is not a knowledge someone is born with, nor is it necessary to succeed in the modern world. It is not taught in school or generally part of a casual conversation.

In other words, it needs to be learned by those wishing to partake in shooting or knowledgeably discuss with experts in the field. As shooters, if we want others to utilize the correct terminology, we need to do two things: first, use it correctly ourselves, and second, share that knowledge with others. Here we will discuss the correct terminology when it comes to ammunition (including the basic parts of ammunition). We break down what each part does and acceptable slang or alternative terms for each.

Is it a cartridge, bullet or ammo?

Ammunition, or ammo for short, is the correct term for the material or projectile expelled by any weapon. If you happen to be using a firearm your ammunition will consist of properly sized cartridges that expel a bullet. However, a crossbow will use a bolt, a slingshot a rock or ball bearing and a catapult… well, anything that will fit into the basket.

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The correct term for a firearm’s ammunition is a cartridge, although acceptable slang terms include round or loud. This cartridge is a pre-assembled ready-to-use type of ammunition designed for modern firearms. Although the term bullet is commonly used to describe a cartridge it is not an accurate replacement for the correct term as the bullet is but one component of the overall cartridge. It is like using the term roof to describe a house or engine to describe an automobile.

So, your rifle needs ammunition to function properly and that ammunition is referred to as a cartridge. That same rifle may fire a bullet, but it is loaded with cartridges, rounds or loads of which the bullet is only one component. If you are buying bullets you will only receive that single component, the projectile, which is only necessary if you are involved in reloading. If you need ready to use ammunition you will purchase cartridges, or ammunition, of the appropriate size.

A round is a single cartridge.

A shell is a type of ammunition fired by larger caliber weapons, usually a cannon or artillery piece. These shells were originally solid pieces, relying on weight and kinetic force to inflict damage. In the mid-19th century, explosives were added to shells and the high-explosive projectile was invented. This is now the standard type of ammunition used in firearms today.

A shot refers to a single firing of a weapons system. Depending on the specific weapons system this could result in the firing of one or more cartridges and the subsequent release of a single or multiple projectiles. “Shot” is also a term that is used to describe a type of ammunition that releases multiple projectiles from a single cartridge such as a shotshell or cluster ammunition.

Basic components of an ammo cartridge

So, now that we understand the correct term for the ammunition used in your firearm is cartridge lets discuss what a cartridge consists of. Most modern cartridges consist of four main components – the case, primer, propellant, and projectile.

A shotgun cartridge, more commonly referred to as a shell, consists of five components – the case, primer, propellant, projectile(s) and wad.

Let’s look at each component of a round, how it functions, and options that may be available:


The casing is the container, or housing, into which all the other components fit. It is the job of the case to hold the other 3 or 4 components in the correct position needed for proper operation.

Early firearms utilized casings constructed of paper, which were then burned or discharged during the firing process.

Modern firearm cartridges utilize a case constructed of metal (brass, steel, copper or aluminum are most common) or plastic (most common in shotgun cartridges).

When selecting a cartridge for your firearm it is vital that you ensure the case is the correct size for the chamber, otherwise you risk malfunction and even a dangerous explosion.

Although the case is commonly referred to as “brass” this term only applies to the expelled cases after they have been fired. Technically, the increased use of metals other than brass have made this slang inaccurate, however, it remains a commonly used and accepted term.

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If you will be reloading you should stick with brass, brass alloy or plated brass. Pure first run brass is best; however, recycled brass can be used as well. In fact, the highest quality brass casings can be reloaded as many as 6 or 7 times. Other forms of brass, including alloys or plated versions, can be used but will have a much shorter life span.


Early firearms relied on gunpowder, which is a specific combination of chemicals that burns rapidly and quickly creates expanding gases as it burns.

Developing the ability to confine and control the burning process and gas expansion was the key to developing reliable, and safe, firearms. Unfortunately, gunpowder is unstable and dirty, capable of exploding or burning easily if mishandled.

Due to its instability gunpowder has been replaced by modern chemical compounds that accomplish the same result without the danger. The most common of these combinations is saltpeter, sulfur, and charcoal. The result is a propellant that burns fast, is reliable and more stable.


The propellant requires a smaller charge to be safely igniting and this is accomplished by the primer.

In modern cartridges, this primer is placed in the rear of the case, either in the rim or a small-cap located at the center, which is activated via a strike of the firing pin.

As is the case with the propellant, gunpowder has been replaced by more stable modern chemical compounds in the construction of the primer.

Quality primers are essential to proper, reliable ammunition performance. A damaged or wet primer will often result in failure to fire or a delayed, hang, fire situation.


Every firearm requires an object that will be expelled from the firearm which will, in turn, be used to hit the intended target.

This object is called the projectile, although the terms bullet, slug or shot are often used in its place. In reality rifles & handguns fire bullets while shotguns fire slugs or shot, the latter being used to describe a group of pellets expelled from a single shell or casing.

Most projectiles are constructed of metal and consist of either lead, steel, tungsten, bismuth or combinations of these metals. Some manufacturers have even experimented with adding a polymer cone to hollow point designs. The result is controlled expansion and deeper penetration.

Bullets, which is an acceptable term for the projectile for most modern firearms, come in a variety of types. Each is designed for a different purpose and may or may not cycle properly in every firearm. Whether you are a hunter interested in greater penetration, a target shooter looking for increased accuracy, or a pinker looking to save some money there is a design that is right for you. Some of the more common types are listed below:

  • Lead Round Nose (LRN)
  • Wad Cutter (WC)
  • Semi-Wad Cutter (SWC)
  • Semi-Jacketed (SJ)
  • Full Metal Jacket (FMJ)
  • Semi-jacketed Hollow Point (SJHP)
  • Jacketed Hollow Point (JHP)
  • Special (RCBD)
  • Soft Point (SP)
  • Armor Piercing
  • Boat Tail
  • Boat Tail Hollow Point
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As discussed earlier a shotgun cartridges includes a fifth component, the wad. The wad is a piece of plastic, or sometimes paper, inserted into the case between the propellant and projectile. The purpose of the wad is to create a more airtight space in which the propellant’ s gases can build when burned and to assist in propelling the projectiles in a uniform fashion.

Putting the basic ammunition round all together

Unless you reload your own ammunition it may appear unnecessary to understand how the various basic parts of ammunition components fit together and work in harmony. However, if you are determined to understand your sport, and be able to speak about it in an informed and accurate manner, this increased knowledge will allow you to do so.

As discussed earlier, the case is the housing into which the other components are housed. In the case of centerfire cartridges (the most common type of modern ammunition) the primer is fitted into a pocket in the base of the case, the propellant is packed into the hollow interior space and a projectile (aka bullet) is secured into the open end. In the case of shotgun cartridges, the wad is placed between the propellant and the projectile(s).

When the trigger is pulled the hammer hits or releases the firing pin. The firing pin, in turn, moved rapidly forward and strikes the primer. Once struck by the firing pin the primer ignites and almost immediately ignites the propellant by allowing a flame to enter the cartridge via a small hole behind the primer cap.

This results in an instantaneous chemical reaction that creates expanding gases which, due to the confined space within the case, cause the projectile to be rapidly expelled. Once expelled from the case the projectile travels down the only path available to it – the firearm’s barrel.

In single action, double action and semi-automatic firearms this cycle repeats each time the trigger is pulled, although each has a different sequence of steps required to allow the trigger to rest between shots. An automatic weapons system will continue to fire, repeating the above cycle uninterrupted until the trigger is released, or the ammunition is exhausted.


There you have it, the main parts of ammunition in a nutshell (or casing is you like). Remember, learning the correct terminology will increase your shooting knowledge. Whether it’s buying 9mm ammo in bulk or just plinking the afternoon away with some cheap 22 LR.

Using correct terminology will allow you to be taken seriously by other shooters. Next time you are at the gun store look around and see what is available, ask questions to learn what is new and what might work well in your firearm. Or, you know, buy ammo online and learn about the rounds from expertly written descriptions.

Of course, every firearm owner has a responsibility to read the owner’s manual and practice safe shooting.

Before you know it, you will be the one others come to for information, waiting patiently while you shoot so they can ask “Is it a bullet, ammunition, or cartridge?”

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Ethan Smith is a seasoned marine veteran, professional blogger, witty and edgy writer, and an avid hunter. He spent a great deal of his childhood years around the Apache-Sitgreaves National Forest in Arizona. Watching active hunters practise their craft initiated him into the world of hunting and rubrics of outdoor life. He also honed his writing skills by sharing his outdoor experiences with fellow schoolmates through their high school’s magazine. Further along the way, the US Marine Corps got wind of his excellent combination of skills and sought to put them into good use by employing him as a combat correspondent. He now shares his income from this prestigious job with his wife and one kid. Read more >>