AR-15 Parts Breakdown [Build List]

If you landed on this article, it might mean that you are attempting one of the most satisfying journeys you can pursue as a shooting enthusiast – building your own AR-15! To build your own AR-15, you need to know the anatomy of the weapon, what goes where, or should I say, what doesn’t go where, what is each of the parts functions, and where they fit in the big picture of your AR-15. Therefore, this guide acts as your build list of what you can upgrade and what to look at when upgrading. Feel free to follow our links for in-depth guides on each significant AR-15 part.

What Are The 4 Groups Of AR-15 Parts?

When dissecting the intricate AR-15 and looking at its anatomy, it is evident that you get four main groups of parts. These four AR-15 part groups are listed below.

  1. Upper Receiver – Forms the top part of the AR-15. A complete upper receiver includes the barrel, handguard, charging handle, and bolt carrier group (BCG).
  2. Lower Receiver Group – Forms the bottom part of the AR-15, including the fire control group, trigger mechanism, magazine well, and provides attachment points for the stock and pistol grip.
  3. Barrel Group – The barrel has a group of its own and includes the barrel nut, gas system, muzzle device, and physical barrel.
  4. Furniture Group – Comprises everything you can further customize for performance and comfort during use, such as stock, grips, handguards, and attachment points for AR scopes, lasers, and flashlights.

AR-15 Parts

1. Upper Receiver Parts

When we further dissect the upper receiver, we get the following parts:

  • Upper Receiver – The physical attachment block for the additional upper receiver parts. It connects to the lower receiver, providing the framework for the entire upper assembly.
  • Barrel – As you already know, the barrel is where the bullet travels upon trigger pull. Its length, twist rate, and material influence the fired round’s accuracy, range, and velocity.
  • Gas Block and Gas Tube – Gas blocks and tubes work together to form the complete gas system of your AR-15. An adjustable gas block diverts some propellant gases from the fired round into the gas tube, which cycles back to the BCG to eject the spent cartridge and chamber the next.
  • Bolt Carrier Group – The BCG is a complex assembly of parts, including the bolt carrier, bolt, firing pin, and other parts. Its main purpose is unlocking and extracting the fired cartridge, ejecting it through the ejection port, and chambering a new round. The BCG group basically functions as the heart of the semi-automatic operation.
  • Charging Handle – This is a manual alternative where you can pull the bolt carrier group back to chamber a new round or clear a malfunction. The charging handle is a lever you can pull to operate the bolt carrier.
  • Forward Assist – A small button located on the upper receiver to ensure the bolt is fully closed and locked in place. This tool ensures the firearm is in battery if you are manually chambering a round.
  • Rail System/Handguard – The handguard and rail system operates as one part, surrounding the barrel and providing a place to attach accessories like AR red dots, light, and grips. The AR15 Handguard also protects your hand from the hot barrel in the event of repeated rapid firing.
  • Ejection Port Cover – The ejection port functions as a small cover over the opening where spent cartridges are ejected from the BCG. It also acts as a debris and dust cover, protecting your rifle when not in use, and contributes to the reliability and longevity of the firearm.

2. Lower Receiver Parts

Looking at the lower receiver, you can expect the following parts:

  • Lower Receiver – Similar to the upper receiver, AR-15 lower receivers are the frame that houses many key components that allow the AR-15 to function. It is even considered the legal “firearm” part of the gun, and you often require a license to purchase it.
  • Trigger Groups – Trigger groups consist of the physical trigger, hammer, sear and other components involved in controlling the firing action of the weapon. When you pull the trigger, the hammer is released and strikes the firing pin to initiate the firing sequence.
  • Lower Parts Kit – Lower parts kit is a package or kit that includes most of the small parts needed to complete the lower receiver assembly, such as magazine release components, bolt catch, springs, guard roll pin or handle latch roll pin, and safety selectors.
  • Buffer Tube / Buffer – The buffer tube is important as it ensures the smooth cycling of the bolt carrier group and the normal functioning of the AR. Its main components – the buffer weight and buffer spring – control the bolt’s rearward travel and help absorb the recoil produced from firing a bullet.
  • Buttstock – The buttstock is an important part of the comfortability, safety, and accuracy of the rifle. It is the part of the rifle you place against your shoulder. A custom buttstock enables you to adjust the buttstock to fit your body and shooting style – offering much better comfort and control.
  • Magazines – Magazines hold the ammunition that feeds into the chamber of the AR-15. You can choose a magazine capacity based on your use case, either opting for quantity or performance (agility and weight).

AR-15 lower receiver parts

3. Muzzle Device Parts

Muzzle device parts are attached to the end of the barrel and have numerous functions, depending on your specific muzzle device. Changing muzzle devices is one of the most popular AR-15 mods shooters make. The three main muzzle devices are:

  • Compensators – This type of muzzle device helps reduce muzzle rise (the upward movement of the gun’s barrel you encounter when shooting multiple rounds). It functions by redirecting gases upward as they exit the barrel, allowing you to maintain optimal target alignment between shots and consequently improving your precision.
  • Muzzle Brakes – Muzzle brakes reduce the recoil produced by the rifle by redirecting the gases to the sides of the firearm. This reduces the backward force applied to you when shooting and allows for better control and comfort during rapid firing. Muzzle brakes are especially helpful to young and inexperienced shooters.
  • Flash Hiders – This muzzle device reduces the visible muzzle flash produced when the gun is fired. Muzzle flash occurs as a result of burning gases exiting the barrel. A flash hider reduces the visibility of the weapon, especially at night. This is an ideal attachment for snipers and tactical officers who don’t want their position to be revealed.

AR-15 lower receiver parts

4. Grip Parts

Grip parts enhance the control, comfort, and stability of your AR-15. This allows you to have better handling of the firearm and create an overall more enjoyable shooting experience. The two main grip types you get are:

  • Pistol Grips – The pistol grip is located at the rear of the lower receiver and is the primary handle that you grasp with your firing hand. This grip is designed specifically to be comfortable and ergonomic, aiding in control, accuracy and reducing the occurrence of “pulling your shots.”
  • Foregrips – Foregrips often don’t come with complete upper and lower receivers. Consequently, you need to buy them separately and attach them to the handguard near the front of the rifle. They are gripped with the non-firing hand and often come in various angles, including the most common, vertical, angled, and, my favorite, a combination of both. Foregrips are great for providing additional control and stability, especially when you are busy with an intense shooting session. These grips help manage vertical recoil and enhance your overall shooting comfort.

5. Accessories

Now, we get to my favorite part of building your own AR-15 – the accessories. These AR-15 parts enhance the functionality, accuracy, and versatility of your AR-15.

  • Red Dot Sights – AR-15 red dot sights provide an easy and rapid point of aim in the form of an illuminated red dot. Red dots are perfect for situations where you need to rely on rapid target acquisition, such as self-defense, competitive shooting, tactical, and even hunting in dense brush. Red dot sights are straightforward and ideal for educating new shooters on how to shoot with an optic.
  • Scope – Moving to more advanced optics, we get AR-15 scopes. These optics introduce magnification to the aiming process, allowing you to spot and identify distant targets with great precision. They rely on a reticle or crosshairs to help you with an accurate point of aim. Scopes are an essential accessory to any AR-15 hunter’s kit and come in various magnifications and designs to suit your specific needs and preferences.
  • Lights & Lasers – Lastly, in the accessory section, we have tactical lights that provide illumination. These lights help in target identification and alignment in low-light conditions. Additionally, lasers act as an additional aiming reference and are even faster than red dot sights. Both these types of illumination are invaluable for self-defense and tactical applications – improving visibility and targeting.

6. Build Tools

If you want to build your own custom AR-15, you’re going to need a couple of tools to help you with the job. Here are the tools I find most helpful when I build my custom ARs:

  • Vise – A sturdy vise is one of the most important build tools you can have in your building tool arsenal. It helps secure all the parts in place, ensuring you don’t make accidental mistakes. It also makes the building process much easier by providing a stable assembly platform.
  • Upper/Lower Vice Block – A vice block is used in conjunction with a vise to hold upper and lower receivers securely without damaging any of the intricate components. This helps to streamline your assembly process.
  • Pin Punches – Pin punches help to insert and remove your AR-15 pins, especially those found in the trigger assembly. Make sure you get the right size pin punches to match the pins used in your AR-15.
  • C-Clamp – In addition to a vice and vice block, a C-Clamp helps to hold parts together tightly during assembly, further ensuring proper alignment and secure connections.
  • Roll-Pin Pusher/Drift Tool – Roll-pin pusher assists in the installation and removal of roll pins. They are vital in ensuring you don’t damage the pins and the surrounding areas when you work with the pins.
  • Armorer’s Wrench – An armorer’s wrench is one of the most helpful tools and can be used on a variety of tasks. It is specifically designed for the AR-15 and can help with the installation and removal of barrel nuts, flash suppressors, and other parts.
  • Utility Knife – No toolbox is complete with a trusty Swiss army knife! You’ll need a utility knife for cutting materials, cleaning certain areas, and trimming or adjusting certain components that may require a scissor or screwdriver.
  • Hex Key Set – Hex keys, also known as Allen wrenches, are essential for installing and adjusting parts of your AR-15 because many parts and accessories are secured with hex-head screws.

What Is The Best Way To Upgrade Your AR-15?

The best way to upgrade your AR-15 starts by identifying what you want to achieve with your rifle. Once you’ve identified your goal, look at the parts that will best help achieve that goal.

For instance, if you want to hunt with your AR-15, you can start upgrading your rifle scope, ar15 trigger types, and barrel. Alternatively, if you want an AR-15 for self-defense, look at attachments like a red dot and laser or flashlight, grips, and muzzle devices.

How Do Rifle Scopes Improve AR-15 Performance?

AR-15 rifle scopes enhance your rifle performance, specifically at long distances. They provide magnification, which enables you to define targets more efficiently beyond 100 yards and shoot more accurately at these distances. Ultimately, they form an integral part of hunting and competition shooting.

How To Modify Your AR-15 So It Performs Better In Low Lighting?

There are a few things you can do to improve your rifle’s performance in low-lighting conditions. The easiest strategy to modify your AR15 is to upgrade your sight by attaching one of the following optics:

  • Use a red dot sight
  • Night vision scope
  • Thermal scope
  • Use a higher-quality rifle scope with a bigger objective lens and higher-quality lens coatings

Alternatively, you can add tactical lights and lasers to your sight to improve low-light performance.

How Do Red Dot Sights Improve AR-15 Performance?

A red dot sight can improve your AR-15 performance in two ways: Increase target acquisition rate by providing a simpler aimpoint with an unobstructed view and improve accuracy with an accurate and easy-to-use red dot. If you want something to improve your AR-15 performance at close to medium ranges, then an AR-15 red dot sight is what you need!

Frequently Asked Questions

How long does it take to build an AR-15?

It depends on the amount of upgrades you want to do. If you have complete lower and upper receivers, it only takes a few hours. However, if you are new or want to build an entire rig, it can take a full day, sometimes even a couple of days.

Can the AR-15 be disassembled into its individual parts?

Yes, one of the most favorable attributes of the AR-15 is its modularity - allowing easy and full disassembly into its individual components.

Is it legal to purchase AR-15 parts without a firearms license in certain regions?

Yes, you can purchase most parts of an AR-15 without the need for a firearms license. However, if you want to purchase a lower receiver or parts of a lower receiver, you require a firearms license.

The Bottom Line

There you have it – the anatomy of the AR-15. While the rifle looks pretty straightforward, it is actually comprised of various integral parts that ensure the smooth functioning of the rifle. This is why the AR-15 is so popular. Each of these integral parts can be upgraded or modified exactly to your needs and use case. However, it is important that you take the necessary precautions before starting the upgrade – talk to a qualified gunsmith, make sure you have the right tools, make sure your accessories match the rail system, etc. In the end, building or upgrading your own AR-15 is a wonderful and satisfying journey that will leave you smiling – if done right!

About the author

Patrick Howard

I have been working as a gunsmith for 20 years. Rain, fog, moisture, high temperature, or even snow are all the things a product must withstand in order to be recommended by me.

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