How Does an AR-15 Work?

February 20, 2023
Natalie Thorburn

The AR-15 is a popular semi-automatic rifle used for hunting, sport shooting, and home defense. “America’s rifle” is lightweight, versatile, and reliable, so it is no wonder that it became a staple in the firearms community.

However, the AR-15 can be a complex weapon for those who are new to firearms. This article will explain how an AR-15 works and what makes it a unique weapon.

But first, let us discuss the history of this rifle and how it evolved into the weapon we know and love.

black and brown assault rifle

[Source: Unsplash]

History of the AR-15

ArmaLite first developed the AR-15 in the 1950s as a military weapon. However, it was not until the Vietnam War that the rifle became widely used by the US military.

Known as the M16, the military version of the AR-15 was fully automatic and had a different design than the civilian version of the weapon.

In the 1980s, the AR-15’s versatility, accuracy, and ease of use made it a popular civilian weapon. Today, it is one of the most popular firearms in the United States, used for various purposes, including home defense, marksmanship competitions, and hunting.

Automatic vs. Semi-Automatic Weapons

We’ve used the terms “semi-automatic” and “automatic” a couple of times in the article, so we should probably explain the difference between the two for those unfamiliar with the terminology before moving on.

A semi-automatic weapon reloads the chamber automatically after each shot, but the user must pull the trigger to fire each round. On the other hand, an automatic gun keeps firing as long as the operator holds down the trigger. These types of weapons are mostly unavailable to civilians in the United States.

Now that we’ve briefly covered the rifle’s history and explained what the term “semi-automatic weapon” actually means, we can move on to the crux of the matter and explain how an AR-15 works. We will discuss the weapon’s construction before moving on to its operation and what makes it unique.

Construction of the AR-15

As mentioned earlier, the AR-15 is a semi-automatic rifle. It comprises two main components: the upper receiver and the lower receiver. These components combine to make the AR-15 and are responsible for its operation and performance.

This section will focus on the construction of the rifle, focusing on the upper and lower receivers and their respective roles.

Upper Receiver

The AR15 upper receiver is the section of the rifle that houses the charging handle, bolt carrier group, and barrel. You can think of the upper receiver as the “heart” of the AR-15 since this is the part of the rifle responsible for firing the round.

Let’s discuss the individual components of the AR-15 upper receiver in a bit more detail.


The barrel of the AR-15, or any rifle for that matter, is the part that the bullet travels through, and it is a crucial factor in the weapon’s accuracy.

The barrel is typically made of stainless steel or chrome-moly steel and is available in various lengths and calibers.

The barrel’s length affects the velocity and accuracy of the round, and the caliber affects the round’s size and weight.

The inside of the barrel is usually rifled to impart spin on the bullet, increasing its stability and accuracy.

Bolt Carrier Group

The AR-15’s bolt carrier group is in charge of cycling the rounds and extracting spent cartridges. It is the component responsible for the rifle’s semi-automatic operation and comprises several parts, including the bolt, carrier, and firing pin.

We will discuss these and other parts further when discussing how the AR-15 operates.

Charging Handle

The charging handle is used to cycle the bolt carrier group manually. It is located on the right side of the upper receiver, and the shooter can use it to check the chamber for any reason or whenever there’s a jam.

Lower Receiver

A rifle’s lower receiver is the part that houses the trigger, magazine release, and other controls. On the AR-15, it is made up of two halves joined together.

The AR-15’s lower receiver houses the magazine and the trigger. As you’re probably aware, the trigger is the part of the rifle that the shooter pulls to fire a round. It is another crucial component in the weapon’s accuracy, which is why the AR-15’s trigger is adjustable and upgradeable.

The magazine release allows the shooter to quickly and easily remove the magazine when empty. The release is located near the trigger for improved ergonomics, meaning it can be operated with the shooter’s trigger finger.

Other Ergonomic Features of the AR-15

The lower receiver of the AR-15 is almost entirely responsible for the weapon’s ergonomics. It can be fitted with different stocks and grips, allowing the shooter to customize the gun to their liking.

For example, the grip (the part of the rifle that the shooter holds) can be made of various materials, including rubber, polymer, and wood.

The stock is the section of the rifle that the shooter rests against their shoulder. It can be adjusted for the length of pull, allowing the user to find the most stable and comfortable position.

Like the grip, the stock can also be made of a wide range of materials and fitted with various accessories, including sling swivels, cheek rests, and butt pads.

Operation of the AR-15

Since the AR-15 is a semi-automatic weapon, users must pull the trigger for each round they wish to fire. When the trigger is pulled, the hammer strikes the firing pin, igniting the cartridge and firing the bullet.

The gas built up by the explosion of the cartridge is funneled into the bolt carrier group through a tube, pushing it rearward. This process extracts the spent cartridge and loads the next round from the magazine into the chamber.

This gas-operated system helps reduce the amount of stress on the moving parts of the AR-15 and makes it a reliable weapon that can fire thousands of rounds without jamming.

AR-15’s Accuracy

There are several factors contributing to the AR-15’s much-lauded accuracy:

  • Barrel — The barrel of the AR-15 is typically made of high-quality steel and rifled to spin the round on its longitudinal axis. The length and caliber of the barrel can also affect accuracy, and it is up to the shooter to choose the barrel form factor that best fits their needs.
  • Trigger — Although it may seem inconsequential to the untrained eye, a good trigger can significantly improve accuracy. The AR-15’s trigger is available in various weights and designs, allowing the shooter to set up the weapon according to their preference.
  • Sight — This is the part of the weapon that the shooter uses to aim at their target, so it is pretty clear why it is a crucial component when it comes to accuracy. The AR-15 can come with a basic iron sight or sport various optics, such as red dot sights, holographic sights, and scopes.


The AR-15 is a versatile and reliable weapon that is used for a variety of purposes. It is made up of two main components, the lower receiver and the upper receiver, which are the heart of the rifle.

This gas-operated, semi-automatic weapon fires one round with each pull of the trigger. It is known for its accuracy, thanks to the high-quality design and build of its barrel, as well as its customizable trigger, stock, grip, and sight.

Whether you’re interested in purchasing a weapon for home defense, hunting, or sport shooting, the AR-15 is worthy of consideration.

Author bio:

Travis Dillard is a business consultant and an organizational psychologist based in Arlington, Texas. Passionate about marketing, social networks, and business in general. In his spare time, he writes a lot about new business strategies and digital marketing for House&Courtyard.

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