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AR-15 Parts Explained

AR-15 | AR Parts | Razorback Armory

Razorback Armory wants to share the breakdown of the AR-15 and all the great ways you can customize it. Firearms require precision and attention to detail, especially if you’re building your AR. Semi-automatic firearms have more crucial pieces and components than other firearms because of their rapid-fire capabilities. In this blog, we will break down the AR-15.

AR-15 | AR Parts | Razorback Armory

AR Customization

Here at Razorback Armory, we supply our customers with the parts and accessories they need to build their firearms. Our firearm parts primarily are made in the USA with top-quality metals to last a lifetime. Not only do we supply the parts to build firearms, but we also provide our customers with pre-built custom guns. If you need recommendations for hand guards, we can’t get enough of the newest addition to the Aero Precision Hand guard lineup, the ATLAS S-ONE. It’s lightweight, made from T-6 aluminum, and manufactured in the U.S.

Trick out your AR with our endless amounts of gun accessories. From grips, triggers, and optics to the bolt carriers, to hand guards, and so much more… we have it all!

AR-15 | AR Parts | Razorback Armory

Lower Receiver

The lower receiver is the registered part of the AR. It’s the base of the firearm and the foundation of your custom build. The lower receiver parts are also where the ergonomics of the firearm come into play.

Some pins are tighter to open than others. You don’t want the pin to be so tight it feels stuck. If you’re out in the field and need to check for an obstruction in the firearm, you’ll need those pins to move somewhat freely.

The Lower Receiver of the AR Contains:

  • Take Down Pins

  • Springs and Detents

  • The Drift Roll Pin

  • Bolt Catch Release

  • Mag Release

  • Fire Control & Safety

  • AR Pistol Grip

  • Stock, Buffer Tube and Spring

If you’re building your AR’s lower receiver and parts kit, TAKE YOUR TIME, and be diligent. When placing springs under tension, you’re pushing parts or pieces across the top of them. Be efficient, diligent, and deliberate, or you’ll have springs and pieces flying across the room!

If you did lose your spring, you’re in luck because Razorback Armory sells springs and other AR accessories.

AR-15 | AR Parts | Razorback Armory

Upper Receiver

Your AR-15’s upper designates your caliber. This will be designated by your barrel where the gas orifices are drilled. The four lengths: pistol, carbine, mid-length, and rifle. Pistol is the shortest, and the harvest of gas is sooner; it is not as smooth as the mid-length or rifle length gas tube.

AR Upper Assembly Contains:

  • Upper Receiver

  • The Barrel

  • Barrel, nut, and handguard

  • Gas Block & Gas Tube

  • Forward Assist

  • Port Door Cover

  • Bolt Carrier Group

  • Charging Handle

  • Muzzle Device

AR-15 | AR Parts | Razorback Armory


When selecting the optics for your AR, we ask our customers, “how do you see yourself shooting the gun?”

If you’re looking for a firearm to have fun with, like shooting steel plates or small objects with your friends, an iron sight is a great choice, or even a SIG Romeo 5. If you’re looking for optics to help with precision and accuracy with the red dot, a SIG Tango MSR is your best bet. The SIG Tango MSR has variable power, 1-6, 1-8, 1-10. If you’re aiming at a closer target, each of those scopes allow you to vary to a lower power to get a better field of view. If you are aiming at an object further away, you can always dial up to a higher power for a more precise shot.

For the people hunting with their AR and need optics for deer and small game, we have traditional scopes with varying magnification.

Interested in learning more about the components of an AR or building an AR? Check out Razorback Armory’s Bullet Points Podcast, streaming on Spotify and Apple Podcasts.

Our mission at Razorback Armory is to supply top-quality firearm parts and educate people on building firearms and gun safety.


Razorback Armory is St. Louis's top full-service firearm shop committed to selling, servicing, handling, repairing, customizing, teaching, researching, idolizing, and generally loving everything guns and ammo. We are more than your typical gun store - we are your locally owned specialized gun store and a knowledge center. We aim to serve our customers with top-notch service and provide the best education and training.


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