In this post we’ll break down the AR into 4 major parts.  You can use this in conjunction with the TERMINOLOGY post (work in progress).  As I make more posts about these specific components, I will link this page to them.

Lower Receiver – Often called the ‘lower’ for short. This is most surprisingly the only part of the AR-15 that requires an FFL dealer to purchase (it has a serial number).  This receiver houses the Trigger Assembly, Magazine, Magazine Release Button, Pistol Grip, and the Safety Selector. Typically these receivers are available to purchase as a ‘stripped’ part (meaning none of the aforementioned components are installed) or a ‘complete’ build having all the components already installed.  For more specifics, go HERE for the post on the lower build.

Upper Receiver – Often called an ‘upper’ for short.  This receiver houses the Bolt Carrier, Bolt, Forward Assist, & Charging Handle.  Just like the Lower, you can purchase these as stripped empty receivers, or as complete builds with all the components already installed.  The Upper comes in a few different variations described in the Upper Detail post.

Stock – Pretty simple in concept. The stock is like any other rifle stock. Available in fixed or adjustable lengths.  The stock assembly houses the Buffer Tube, Buffer Spring, & Buffer assembly.  Some stocks have nifty little storage compartments for ammo or gadget batteries.

Barrel – Barrels come in a variety of lengths and styles.  Typically, this forward section of the rifle has a Flash Hider on the muzzle, a Hand-guard for a place to grip and place accessories, the Gas Return Tube, and the Gas Block.  It is important that if you choose an M4 style barrel that you make sure to have a matching Upper Receiver. Again, see the M4 post for details

Moving Animation:

Bushmaster posted this really cool animation which shows you the mechanical functions of all the working parts.  I’m an ‘engineer’ at heart, so seeing how all these pieces interact with each other was very educational.  Click the image below to check out the animation!