woman shooting AR 15 outdoors

The AR-15 rifle is a versatile and widely used firearm known for its modularity and customization options. Understanding its components is essential for both enthusiasts and newcomers alike. In this guide, we’ll give you a comprehensive breakdown of the parts of a AR 15 so you can have a better idea of your options. 

AR 15 Parts Breakdown

The parts of a AR 15 can generally be grouped into three categories: upper, lower, and muzzle. 

Upper Parts of a AR 15

Upper Receiver

The upper receiver houses the bolt carrier group (BCG) and barrel. It also includes the forearm and charging port.

image of the upper receiver of an AR 15
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The barrel determines the rifle’s accuracy and range, making it one of the most critical parts of a AR 15. Barrels come in various lengths, weights, and materials. Generally, longer barrels are more accurate, while shorter barrels are easier to maneuver. The minimum length for a rifle is 16 inches for civilian shooters. Any shorter will require special permits and a short-barrel federal tax stamp. 

barrel of an AR 15 rifle
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Bolt Carrier Group (BCG)

The BCG is responsible for loading, firing, and ejecting spent cartridges. It consists of the bolt, bolt carrier, gas key, firing pin, cam pin, and extractor, along with other small parts. You have the option of buying a pre-assembled BCG or building one from scratch. 

LanTac USA LLC, 556 Enhanced BCG

Ejection Port Cover

This is another on the list of essential parts of a AR 15. It has a simple, but critical function: to prevent dust and dirt from getting into the bolt carrier group and upper receiver. You manually close the ejection port cover, which opens each time the BCG moves to the back. 

Luth-AR, .308 Ejection Port Assembly

Handguard and Rail System

The handguard and rail system provide both a gripping surface and protection from the barrel’s heat. They also serve as a mounting platform for accessories such as optics, lights, lasers, sights, and grips.

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Gas System

AR 15’s use gas to facilitate their semi-automatic capabilities. When you pull the trigger, gas cycles through the bolt carrier group from behind the bullet, through the gas port, down the gas tube, and through the gas key. AR 15’s use either direct impingement or gas piston systems. In general, piston systems are favorable, because direct impingement leads to a lot of fouling, build up, and oil. 

Lower Parts of a AR 15

Lower Receiver

The lower receiver contains the trigger group, magazine well, and controls such as the safety selector, magazine release, and bolt catch. Of the parts of a AR 15, the lower receiver is the most regulated, since it constitutes the actual “firearm.” 

Aero Precision, M4E1 Complete Lower Receiver

Trigger Group

The trigger group includes the trigger, hammer, and disconnector. It controls the firing mechanism and reset. Of all the parts of a AR 15, the trigger group is one of the most important when it comes to your overall shooting experience. Lighter weight triggers are often faster and more accurate, but their ease-of-use also increases the likelihood of a negligent discharge. You will need to find the trigger that is most comfortable and reliable for you. 

trigger system for AR 15 competitive shooting
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Buffer Tubes

The buffer tube houses the recoil buffer and spring, which absorb recoil and cycle the action.The right buffer tube can help you shoot more accurately and for longer, while also protecting the faster moving parts of the weapon.  

black mil-spec buffer tube
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The stock provides stability and support for the shooter. It can be fixed or collapsible. Fixed versions are generally better for steading heavier and longer AR 15s, while collapsible ones are preferable for lighter weapons. 

Hogue, AR-15 6-Position Stock, Collapsible


The grip provides a comfortable and ergonomic hold on the rifle. Your pistol grip will be attached to the lower receiver. You may also want to consider a foregrip, which helps steady the gun further. Foregrips can be angled or vertical depending on your personal preference.  

Ergo Grip, ERGO 2 with SUREGRIP in beautiful robin’s egg blue

Muzzle Devices

A few parts of a AR 15 are found directly on the muzzle. These are collectively known as “muzzle devices” and are designed to enhance various aspects of the AR 15’s performance:

Flash Hiders

Flash hiders, also known as flash suppressors, are designed to reduce the visible flash produced when firing the rifle. They work by dispersing the burning gasses that exit the muzzle, reducing the brightness of the flash visible to the shooter and nearby observers. This feature is particularly beneficial in low-light conditions or when maintaining a low profile is essential. Flash hiders come in various designs and can also serve as a mounting point for suppressors or other muzzle devices.

Muzzle Brakes

Muzzle brakes are designed to reduce recoil and muzzle rise by redirecting the gasses expelled when firing the rifle. They typically feature baffles or ports that direct the gasses sideways and/or rearward, countering the upward movement of the barrel during recoil. This results in reduced felt recoil and improved control, allowing for faster follow-up shots and greater accuracy, especially in rapid-fire scenarios. 

Keep in mind, however, that muzzle brakes can increase the perceived noise and muzzle blast experienced by the shooter and those nearby. If they are the kind that eject gasses horizontally, you may also wish to avoid them at a crowded range out of respect for the other shooters.


Compensators, also known as muzzle compensators or recoil compensators, are similar to muzzle brakes but primarily focus on mitigating muzzle rise. They achieve this by directing gasses in specific directions to counteract the upward movement of the barrel during firing. Compensators are particularly popular among competitive shooters and those seeking to improve their shooting performance by minimizing muzzle movement between shots. While compensators can effectively reduce muzzle rise, they may also increase the perceived noise and muzzle blast compared to other muzzle devices.


This handy gun cleaning mat by Tekmat lists all of your AR 15 components to ensure you maintain every part.  

Related: Do You Need a Gun Cleaning Mat?

AR 15 Building for Beginners

Building an AR-15 rifle can be a rewarding experience, but it requires knowledge and skill to ensure safety and functionality. Even if you are a seasoned shooter, a class can refresh your knowledge and inform you of the latest rules and regulations concerning parts of a AR 15. 

Enrolling in an AR-15 building course offers several benefits:

Hands-On Experience

Courses typically provide hands-on instruction, allowing participants to familiarize themselves with each component and its assembly in a safe environment.

Safety Education

Understanding how to assemble and disassemble an AR-15 promotes safe handling practices and firearm maintenance, ensuring responsible gun ownership and the integrity of your weapon.


With so many options out there, it can be difficult to know where to start and which parts to select for your specific needs. A class can help you select the right components to suit your goals, from sport shooting to hunting.  

Legal Compliance

Certain parts of a AR 15, such as the lower receiver and the magazine, are subject to legal regulations that can vary from state to state. An AR build class will make sure your weapon is in compliance with local firearm laws.  

Community Engagement

Learning to build an AR 15 is fun! Building courses provide an opportunity to connect with fellow enthusiasts and share knowledge and experiences. You can learn new customization techniques from each other and show off your latest builds. 

AR Build Class in Omaha

At The Marksman Indoor Range, we offer a variety of courses tailored to all levels. One of our most popular classes is teaching you how to build your own AR 15. The class is spaced over two days to provide you with ample learning time from our highly qualified instructors. As a student in our AR build class, you will also have access to special discounts on parts! These classes fill up very quickly, so be sure to visit our courses page to register for the next one. 

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Heather Kleinman

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