Gun Anatomy: The Basic Parts Of A Gun

By Aaron Spuler | November 3, 2021

Gun ownership comes with plenty of responsibility. The ability to properly care for, maintain, and clean your firearm is crucial, as is knowing when a component isn’t functioning as it should. This is where gun anatomy comes in.

As a lot of firearms have different parts and cycle differently, this guide focuses on one of the most well-known weapons in western countries, the AR-15. The AR-15 consists of 4 main groups, which we’ll discuss below.

Lower Receiver Group

The lower receiver group is largely considered to be the makeup of the actual gun. The following are the main parts that make up the lower received group:

  • Lower receiver – The main part of the AR-15 and the part that’s considered the actual firearm. The lower receiver is the most regulated part of the weapon system, as this is where you will find the weapon’s serial number. AR-15s are widely considered to be a very modifiable gun. This is true for everything except for the lower receiver.
  • Trigger group – The trigger group consists of the trigger, hammer, the trigger sub-assembly and many other small springs and housing components. Triggers are generally very modifiable, with different sizes and weights available.
  • Magazines – Magazines are a simple mechanism designed to hold bullets and provide pressure to the exit, allowing the gun to cycle a new bullet when one leaves the chamber. Magazines come in a variety of materials, sizes and shapes. AR-15 standard-issue magazines are often 20 to 30 round steel STANAG magazines.
  • Buffer tube – seated inside the buttstock, the buffer tube contains the buffer and buffer spring. The main purpose of a buffer tube is to decrease the recoil on firing and decrease the instant shock on the weapon’s components. The instant shock when firing can damage the weapon’s finer components over long periods of time, the buffer tube will help prolong the life span of the weapon.
  • Buttstock – The buttstock is how you shoulder the rifle. Buttstocks are one of the most common modification points of an AR-15, as different people prefer different lengths and heights of buttstock. To tailor a rifle to your preference, the buttstock is one of the first points to address.

Upper Receiver Group

The upper receiver group carries parts that actually fire the bullet and cycle in a new round; between the upper and lower receiver, we find the bulk and all the actual working parts of the gun.

  • Bolt carrier group – The bolt carrier group is responsible for firing, ejecting spent casings, and loading the next road. Consisting of the bolt, firing pin, extractor, gas key and cam pin, the bolt carrier group is the biggest selection of moving parts. Weapon malfunctions are often caused by misalignment, dirt or incorrect tolerances in the bolt carrier group.
  • Ejection port – The ejection port cover is a small cover on the side of the weapon that remains closed until the weapon fires. Spent casings are ejected out of the ejection port. The main purpose of the ejection port cover is to keep dirt and debris out of the bolt carrier group, as this leads to malfunctions.
  • Charging handle – The charging handle is your manual control of the bolt carrier group. Pulling the charging handle back will pull the bolt carrier group back, ejecting anything currently in the chamber and on return, loading a new round. Charging handles are mainly used in 3 situations:
    • Initial load – Once a fresh magazine gets loaded into an empty gun, the charging handle racks the first round into the chamber.
    • Malfunction – If the weapon were to malfunction, the charging handle can clear a possibly malfunctioning round from the chamber and load a new round.
    • Finishing – When done shooting, and the magazine removed, the best practice is to use the charging handle to ensure there’s no bullet in the chamber before stepping away from the firing position.
  • Gas system – The gas system comprises the gas block, gas tube, and gas port. The gas system operates by using spent gas from a fired round, recirculating it back to push the bolt carrier group back and cycle another round. The gas system and the pressure it uses is one of the most important parts to keep your semi-auto or full auto rifle operating seamlessly.
  • Barrel – The barrel of the AR-15 is, in essence, what keeps the bullets going straight and allows the gas system to function as it should. Barrels come in many available lengths. As standard, the AR-15 is released with 16-inch, 20-inch and 24-inch barrels.
  • Forward assist – Forward assist is a back-up in the event that the bolt carrier group does not push forward as it should while loading a new round. This is only a back-up measure to ensure quick clearing of any issues if they were to arise in the field. The forward assist does add some dependability to the rifle. It is, however, viewed by many as unnecessary and more of a cosmetic feature.
  • Handguard – The handguard is a specifically designed shroud to allow the shooter to grip the front of the gun for stabilization while shooting. On the AR-15, the handguard plays more of a role as it plays host to a rail system. The rail system on a handguard is versatile in having a Picatinny or Weaver style of rail which can mount any attachment you could need. Bipods, sights, foregrips, lights, and many other attachments fit seamlessly onto these rail systems.

Muzzle Devices

A muzzle device is a device mounted on the end of the barrel to alter the firearm’s characteristics in a certain way:

  • Muzzle brake – A muzzle brake pushes gasses up and out to lower the amount of recoil felt by the user. Better muzzle brakes will allow for more consistent and accurate shots.
  • Flash hiders – A flash hider exists to reduce the amount of flash or fire at the end of the barrel. A large flash can not only give away your position while in the field but also be a hindrance for users in low light conditions.
  • Suppressor – Suppressors are used to lower the sound of the shot. It’s important to note that most ammunition is supersonic, so will still involve a sonic boom when fired. The suppressor is used more to aid in lowering the volume of the initial shot when the bullet is fired.

Grips

One of the simplest, yet most important parts of any weapon system is how you hold it. Pistol grips and foregrips not only dictate how comfortable the weapon is but also your speed and accuracy while using it. The grip on an A-15 can be customized with rubber sleeves or other materials that improve your control when lining up and firing.

Understanding the AR-15’s anatomy not only means that you can enjoy the best possible performance from every shot, but that you can also store it securely and safely too. You’ll keep it in tip-top condition and can quickly tell if it needs maintenance or is misfiring.

Meta title: The Basic Anatomy Of A Firearm Made Easy | Weapon Blog

Meta description: Learn about the basic parts that make up a gun. Our guide to AR-15 anatomy tells you all about the various components that make up this firearm.

This guest article was written by Naomi Phillips. Naomi is a content writer who’s always on a mission to keep on learning. Thanks to her curious brain and extraordinary ink-slinging, she has written articles covering a broad range of topics—from home safety to jewelry. Naomi has a backdoor garden where you’ll find her during the weekends, tending to her begonias and marigolds.

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