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AR 15 Parts Breakdown, photo

AR-15: Detailed Guide to Understanding Each Component

As one of the most popular American rifles, the AR-15 is a cornerstone of firearm customization. Whether you’re new to guns or a seasoned veteran, modifying your AR-15 rifle is always a joy.

The AR-15 has been constantly hogging the aftermarket spotlight, and you can almost always find the part you’re looking for if you browse hard enough in the stores.

In today’s AR-15 parts guide, we’ll take a look at the prospect of “AR-15 parts explained” as we dive deep into the anatomy of the AR-15 rifle.

We’ll talk about the AR-15’s main components, what they do, where to find them, and differentiate their characteristics.

At the end of this AR 15 parts diagram, you’ll be equipped with the proper, in-depth knowledge about the parts of an AR 15 rifle.

Let’s begin from top to bottom.

Upper Receiver Group Parts

The AR-15 rifle is divided into an upper receiver and a lower receiver.

Some folks like to buy a complete kit from the gun store with an upper and lower receiver.

Others make do.

For those of you who like to take the fun road home, let’s take a look at what constitutes the upper receiver group of the AR-15.

If you want to make your rifle versatile, convenient, and accurate, you best begin learning all the important details of your upper configuration. This includes AR 15 parts names like:

  • Upper receiver;
  • Barrel;
  • Gas block and gas tube;
  • Bolt carrier group;
  • Charging handle;
  • Forward assist;
  • Rail System (Handguard);
  • And ejection port.

This is the general definition of what constitutes an upper receiver, and that’s why it’s called an “upper receiver group”.

The group consists of the upper, barrel, BCG, handguard, charging handle, and other components.

Let’s check the parts out.

Upper Receiver

The upper receiver houses the bolt carrier group, forward assist, dust cover, and charging handle.

It’s connected to the barrel and forend.

It’s fully assembled when you attach a bolt carrier group and charging handle on one side, and a barrel, handguard, and stock on the other.


The barrel of your AR-15 rifle is commonly around 16 to 22 inches. Anything shorter than that is a short-barreled rifle or SBR.

If you’re looking for reliable and lightweight barrels with quality gas systems and rifling, go for button rifling/cold-hammer-forged barrels. They are costly but well worth the price.

Gas Block and Gas Tube

The gas block and gas tube are the gas system components that are responsible for the AR-15 rifle’s cycling operation. It’s the “life force” of the rifle.

The gas block regulates the gas flow from the barrel to the gas tube and receiver, which propells the BCG backwards.

The gas tube is connected to the gas block, and it enables gas passage to the bolt carrier group, minimizing gunk accumulation within the gas system and reducing recoil. This ensures smooth cycling.

There are different gas tube lengths like rifle-length, mid-length, carbine-length, and pistol-length gas tubes, and all of them offer a variety of performance characteristics

A standard factory gas block is good for factory-made ARs, but the fancy custom builds with different BCG models and buffer weights just work better with adjustable gas blocks. They offer better gas cycling control.

Bolt Carrier Group (BCG)

The BGC governs the semi-automatic operation of your AR-15. It handles the bullet loading, firing, and spent round ejection.

Gas-operated BCGs function through a direct impingement gas system that offers speed and reliability.

The BCG comprises essential components like the firing pin, bolt, cam pin, extractor, and gas key.

You can either purchase a pre-assembled BCG like most shooters. Or, you can build it yourself, but this is reserved only for seasoned veterans.

We suggest you consult with your local gunsmith for price comparison. Otherwise, you can’t go wrong with Titanium Nitride parts.

Charging Handle + types of them

Known as the operating handle, the charging handle pulls the BCG backward which prompts it to remove and load rounds into the barrel.

Charging handles can either come in standard model types, ambidextrous, with extended handles, or other modified versions that offer convenience and comfort.

Forward Assist

The forward assist acts as a ‘savior’ when your gun malfunctions. It serves as a nifty tool that pushes the bolt to close all the way back into the rifle, ensuring proper functionality.

Most shooters aren’t too fond of the forward assist, but tactical enthusiasts really appreciate the forward assist for its use in reliability during harsh weather or muddy situations.

Rail System or Handguard

The rail system or handguard comprise the skeleton AR 15 parts that hold together important parts like optics, receivers, and accessories.

As the name says, the handguard protects your palms from the heat from the rifle while you shoot.

Drop-in handguards are easy to implement and are lightweight, but they can be very flimsy, so be mindful of hot and humid temperatures.

Floating handguards, on the other hand, are aluminum-made and are more durable, but more expensive.

Ejection Port Cover

Located on the AR-15 rifle’s right side, the ejection port cover ejects casings after firing. It usually remains closed to protect the rifle from gunk, dust, and debris.

Muzzle Devices

The muzzle devices help with calibrating the gasses that cycle your rifle, and they can also suppress the heat and flash from firing. There are also silencers that lower noise, but they aren’t generally regarded as muzzle devices.

There are three types of common muzzle devices:

Compensators: Compensators make sure your gun points on target instead of going up when you shoot. This is to improve your control and accuracy. The compensator can vent gasses from the barrel upward, and this makes sure the barrel remains straight by force instead of instigating barrel rise.

Muzzle brakes: The muzzle brake lowers recoil by venting the gasses on the sides of the barrel end. Similarly to the compensators, a muzzle brake uses the gas force to help maintain control during shooting.

Flash hiders: As the name suggests, flash hider hides the blinding light when you’re shooting. This is a very important part, especially when you’re shooting at night when the flash is super bright and distracting.

Lower Receiver Group Parts

The lower receiver group is connected to the upper receiver group, and both systemic components complete the rifle.

Lower Receiver

The lower receiver includes the trigger, buffer kit, magazine, buttstock, pistol grip, and all other parts.

Trigger Groups

The AR-15 rifle enjoys a wide plethora of trigger groups. Trigger groups house your trigger, the hammer, and the internal mechanism that allows you to shoot.

If your trigger is too light or too heavy, this affects your stability and, thus, accuracy. It’s important to customize your trigger while minding negligent discharge and the need for fast follow-up shots.

Triggers are generally sorted in multiple groups, including single-stage triggers, two-stage triggers, binary triggers, and adjustable triggers.

Buffer Tube

The buffer tube is a component that helps your recoil system absorb the force, allowing for more controlled shooting.

The buffer tube houses the buffer and the buffer spring, and they both work together to slow down the fast-moving parts of your rifle to ensure better control and smoothness.


This is where you keep your bullets. Magazines are the storage components of the AR-15 bullets.

Magazines for the AR-15 rifle come in 20, 25, or 30 rounds, and it’s usually the 5.56 NATO variations of the caliber. 

There are two types:

Polymer magazines: Lightweight and common, these magazine types never rust and are good for all kinds of weather conditions. You also have some see-through polymer mags that help you see how many bullets are left. Be warned, they break easily.

Aluminum or metal magazines: These mags are durable and robust, but they can rust and are prone to malfunctions in dusty terrain.


The buttstock is the part that’s way back from the rifle. It’s an overlooked component that helps with stability, comfort, and lowering recoil.

A proper buttstock enhances the overall shooting experience, so make sure the buttstock isn’t too short, too long, too narrow, or overly heavy for optimal performance and comfort.

The buttstock falls under two categories:

Fixed stock: Fixed stocks, as the name suggests, are attached to the rifle, and offer robust support in contrast to collapsible/adjustable stocks. They are perfect for managing heavy front-end weight. Their rigidity offers stability and consistency.

Adjustable stock: You can adjust these stocks according to the length you prefer, and most of these stock types offer 5 to 7 different length positions.


They help you hold the rifle with ease, comfort, and stability. It’s the textured, rubber, or polymerized material responsible for how you handle and maneuver the gun. A good grip ensures you shoot accurately, but a better grip helps soak up recoil so your hand won’t hurt.

There are many grip types, but the two most common ones are

Pistol Grip: The classic pistol grip offers great trigger comfort and control. With a vast grip aftermarket, you can easily find a pistol grip that both feels and looks alright. Most shooters stick to one pistol grip their whole life. This is understandable because anything else feels weird and wrong once your hand gets used to a specific type. Try to find your own and experiment before sticking to one kind for a long time.

Foregrip: A secure hold on the rifle’s long barrel is essential besides the pistol grip. This is where the foregrip comes in. A foregrip enhances control and minimizes recoil, which can impact your shooting accuracy and control. Pair a decent pistol grip with a sturdy foregrip for stability, and you’ll have an enjoyable, maneuverable combo. Opt for vertical or angled foregrips to match your shooting style for a competitive advantage.

The Interworking of All AR 15 Components: How Does It Function?

Most standard AR-15 rifles operate via a gas system. Here’s the full process:

  1. When a round is fired, the gas is captured and helps cycle the rifle.
  2. This gas travels through the barrel which is redirected by the gas block and gas tube.
  3. The gas pushes the bolt carrier group (BCG) back, ejecting the spent cartridge through the upper receiver opening.
  4. A spring in the buffer tube pushes the BCG forward, loading a new round from the magazine into the barrel.
  5. This process also ejects spent rounds and replaces them with fresh ones, allowing for continuous firing.

This is what makes the mechanism so ingenious; all of its kinetic energy is of use, and the gas-operated system allows for reliable and fast shooting.

In simple terms, the gas-powered mechanism in the AR-15 makes it fire, eject, and reload with each shot.


The AR platform is as versatile as they come. If you’re trying to graph the AR 15 list of parts, we certainly hope that this guide helped you a little.

One of the most important characteristics of the AR-15 is that you can assemble, construct, modify, and clean the rifle with very simple tools and little effort. This is what makes the AR-15 rifle so fun.

Hopefully, this AR 15 parts breakdown guide has shown you what you can do and where to start when building your own platform.

Stay safe, shoot straight!

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