How Does an AR-15 Work?

By Berry Mathew

The AR-15 is not just any rifle; it is a legend. 

It is a weapon that evokes a sense of power, precision, and awe in those who wield it. It is a rifle used for everything from hunting to home defense and is a staple of American gun culture. Its versatility and reliability have made it one of the most popular firearms in the country, and its design has inspired countless other rifles.

But what makes the AR-15 so special? How does it work? In this blog post, we will delve into the mechanics of the AR-15, exploring its gas-operated, semi-automatic system and modular design. 

We will examine the direct impingement gas system that makes it such an efficient and accurate weapon, and we will explore the ways in which the AR-15 can be customized to fit the unique needs and preferences of its user. 

So join us as we take a closer look at one of the most iconic rifles in American history and discover the secrets that have made it a favorite of gun enthusiasts around the world.

History of the AR-15

The AR-15 was first developed in the 1950s by Eugene Stoner, a former Marine who worked for the ArmaLite Corporation. The original design was called the AR-10, and it was a lightweight rifle that was intended for military use. The AR-10 was chambered in 7.62x51mm NATO and was designed to be used by soldiers who needed a lightweight and accurate rifle that could fire in fully automatic mode.

The AR-15 was developed from the AR-10 and designed to be a lighter and more compact version of the original rifle. The AR-15 has chambered in .223 Remington, which is a smaller caliber than the 7.62x51mm NATO used in the AR-10. The AR-15 was also designed to be used in semi-automatic mode only, which means that it fires one round every time the trigger is pulled.

How the AR-15 Works

The AR-15 is one of the most popular and versatile rifles in the United States. Its gas-operated, semi-automatic system and modular design have made it a reliable and accurate weapon for hunting, target shooting, and home defense. 

Gas-Operated, Semi-Automatic System

The AR-15 is a semi-automatic rifle, which means that it is designed to fire one round every time the trigger is pulled. The rifle is also gas-operated, which means that it uses the gas from the burning gunpowder to power its firing mechanism. When the trigger is pulled, the firing pin strikes the primer on the back of the cartridge, which ignites the gunpowder and propels the bullet out of the barrel.

The gas from the burning gunpowder is redirected through a gas port in the barrel and into the gas block. The gas block is located at the front of the rifle and serves as a junction between the barrel and the gas tube. The gas then enters the gas tube, which is a long, narrow tube that runs from the gas block to the rifle’s upper receiver.

The gas tube directs the hot, pressurized gas into the bolt carrier group located in the upper receiver. The bolt carrier group is responsible for extracting the spent cartridge case from the chamber, ejecting it from the rifle, and loading a new cartridge into the chamber.

As the hot gas enters the bolt carrier group, it pushes against the bolt carrier, which causes the bolt to rotate and unlock from the barrel extension. The bolt carrier then moves rearward, pulling the spent cartridge case out of the chamber and ejecting it from the rifle. As the bolt carrier moves rearward, it compresses the buffer spring located in the buffer tube.

Modular Design

One of the key features of the AR-15 is its modular design. The rifle can be easily disassembled and reassembled, which makes it easy to clean and maintain. The modular design also allows the shooter to customize the rifle to fit their specific needs and preferences.

The upper receiver of the AR-15 can be easily swapped out for a different one, like these Gisele upper receivers. This allows the shooter to change the caliber of the rifle. The barrel can also be easily changed, which allows the shooter to change the length of the rifle and the type of ammunition it can fire.

The AR-15’s lower receiver is also modular, which means that it can be easily customized with different grips, stocks, and triggers. This allows the shooter to tailor the rifle to their specific shooting style and preferences.

Direct Impingement Gas System

Another key feature of the AR-15 is its direct impingement gas system. This system is simple and efficient, and it helps to reduce the amount of recoil that the shooter feels. The direct impingement gas system also helps to reduce the amount of carbon buildup in the rifle, which can cause malfunctions and reduce accuracy.

In a direct impingement gas system, the gas from the burning gunpowder is directed into the bolt carrier group, where it powers the firing mechanism. This contrasts with a piston-driven system, where the gas is directed into a piston that powers the firing mechanism.

The direct impingement gas system of the AR-15 has a few advantages over a piston-driven system. First, it is simpler and requires fewer parts, which makes the rifle lighter and easier to maintain. 

Second, it helps reduce the amount of recoil that the shooter feels, making the rifle easier to shoot accurately. 

Finally, it helps to reduce the amount of carbon buildup in the rifle, which can cause malfunctions and reduce accuracy over time.


The AR-15 is a highly versatile and reliable rifle that many gun enthusiasts love. Its gas-operated, semi-automatic system makes it a precise and efficient weapon for target shooting, hunting, and home defense. 

The AR-15’s direct impingement gas system and modular design make it a durable and customizable rifle that can be tailored to the user’s specific needs.

However, it’s worth noting that the AR-15 has also been at the center of controversy due to its association with mass shootings in the United States. Some people believe that the AR-15 and other similar weapons should be banned or heavily regulated in order to reduce gun violence. Others argue that the AR-15 is a legitimate tool for self-defense and sport shooting and that banning it would be a violation of the Second Amendment.

Regardless of your opinion on the AR-15, it’s important to understand how it works and what makes it such a popular and effective rifle. Whether you are a gun enthusiast, a hunter, or a concerned citizen, knowledge about firearms can help you make informed decisions about gun ownership and gun laws.