The AR15 platform is the most popular rifle system for people to study. There are plenty of materials and data to help us understand its design and parts functionality.
This guide delves into the basics of AR15 Anatomy and parts breakdown, so you know exactly what each part does and how to fix them if they are broken.
AR15 Main Components Breakdown
The AR15 rifle, first designed in the 1950s by Eugene Stoner for ArmaLite, has become a favorite for many. Colt later acquired the rights and introduced it to the military as the M16.
Over time, the AR15 has transformed into a versatile firearm, with numerous parts and accessories available for customization.
AR15 Lower Receiver: This is the bottom half of the rifle and is considered the "firearm" by legal definitions. It houses the trigger assembly, magazine well, and the pistol grip. It connects to the upper receiver and provides mounting points for the stock and buffer tube. Buy AR15 lowers here
Upper Receiver: The upper half of the rifle, it contains the bolt carrier group, charging handle, and the barrel. It also has a rail system on top for mounting optics and other accessories. Buy AR15 uppers here
Barrel Nut: This component secures the barrel to the upper receiver. It also provides a mounting point for the gas tube and the handguard.
Gas Block: Positioned on the barrel, the gas block collects some of the gas from the fired round. This gas travels back through the gas tube into the bolt carrier group, cycling the action.
Muzzle Device: Attached to the end of the barrel, muzzle devices can be flash suppressors, muzzle brakes, or compensators. They help reduce muzzle rise, flash, or recoil.
Anti Walk Pin: These pins ensure that the trigger and hammer pins don't move out of place during firing. They're especially useful for rifles with a high rate of fire or those using certain aftermarket triggers. Buy replacement here
Pistol Grip: This is the handle of the rifle, where the shooter's dominant hand grips the gun. It provides control and stability during shooting.
Trigger Guard: A protective barrier around the trigger, it ensures that the trigger isn't accidentally pulled.
Castle Nut: This nut secures the buffer tube to the lower receiver. It's essential for ensuring the stability of the stock with the option to stake.
Rifle Stock: Attached to the end of the lower receiver, the stock rests against the shooter's shoulder, providing stability and aiding in recoil management. Buy ultra lightweight stock here
M1913 Picatinny Rail: A standardized mounting platform, the Picatinny rail allows for the attachment of various accessories like optics, sights, and lasers.
Quick Detachment Points (QD Points): These are attachment points on the rifle where slings or other accessories can be quickly attached or detached.
M LOK: A modular locking accessory mounting system developed by Magpul. It allows for direct attachment of accessories without the need for rails.
KeyMod: Another modular mounting system, KeyMod has keyhole-shaped slots that allow users to attach accessories at various points on a handguard without rails.
Charging Handle: This part manages the bolt carrier group. It can charge the rifle, lock or release the bolt, and clear any issues. Buy charging handle upgrades here
Fire Selector: This is for safety. It can switch the rifle to safe mode, semi-automatic mode, or even full auto/burst mode, depending on the model. It basically blocks the trigger bar movement when on safe. Buy 45/90 safety selectors here
Trigger System: The AR15's trigger system is straightforward. In semi-auto mode, one pull equals one shot. Full auto and burst modes work a bit differently, with mechanisms to allow continuous firing or limited bursts. Upgrade AR15 triggers here
Bolt Carrier Group (BCG): Think of the BCG as the rifle's heart. It contains essential components that allow the rifle to function, like the firing pin and the bolt. It's crucial to keep this part clean. Buy AR15 bolt carrier group here
Bolt Catch: This small part can lock or release the bolt carrier group, essential for safety checks, reloads and clearing malfunctions.
Magazine Release: Simply a button to release the magazine.
Buffer Assembly: This contains the recoil spring and buffer, which help return the bolt carrier group to its place. Upgrade AR15 buffer system here
Gas System: The AR15 uses a direct impingement gas system. This system uses gas from the fired round to cycle the bolt.
Piston Driven AR15: These reduce heat and residue in the main receiver, extending the bolt's life.
Barrel: The barrel is vital for the AR15. Its length can influence bullet performance. Longer barrels, like 18" or 20", are better for long-range shooting. The twist rate of the barrel also matters, affecting how fast the bullet spins.
Bufferless AR15: This design removes the fixed buffer tube system, allowing for features like folding stocks. Most are piston design
Magazine: The magazine is a detachable container that holds and feeds ammunition into the firearm. For the AR15, magazines come in various capacities, typically ranging from 10 to 30 rounds or more. Spring tension and follower alignment can affect smooth feeding if worn out. Buy reliable magazines here