In this post I’ll go over all the specific parts of the Lower Receiver and Stock / Buffer Assembly.  Click this post or the ‘continue reading’ link below to see the full details.

Assuming you’ll be assembling your AR and not purchasing any ‘pre-built’ parts… This post should go over everything you need to get what it looks like.

Stripped Lower Receiver

This is the only part of the AR with a serial number and is required to be purchased through a FFL dealer.  The stripped lower won’t have any parts installed. I’ve seen these run from $90 to $200 depending on brand.

Lower Parts Kit

The lower parts kit contains all the parts needed for your stripped lower above. I’ve seen these kits sell from $55 to $100.

  • Magazine Catch / Release Button
  • Bolt Catch
  • Pivot Pin / Takedown Pin
  • Trigger Group
  • Safety Selector
  • Pistol Grip
  • Trigger Guard

Pre-built Trigger Groups

Additionally, there are a number of high-quality trigger groups available online. These are built as drop-in style kits that get held in place with the trigger pins as opposed to having to assemble it using your lower parts kit.

Buffer Tube Assembly / Lower Receiver Extension Assembly

The Buffer Tube Assembly is pretty simple… The tube houses the spring and actual weight filled buffer.  These provide a forward force on the bolt after a discharge allowing the bolt to slide a new round into the chamber.  The Endplate holds the Takedown Spring and Detent in place in the Lower Receiver.  As you may have guessed, the Nut holds it all in place.  These buffer tubes come in 2 different sizes, Mil-Spec & Commercial-Spec.  Make sure sure your buffer tube and stock meet the same specifications. Check out the Mil-Spec vs. Commercial-Spec post for specific details on the difference.  The going price for this kit appears to run from $50 to $100.


The buttstock should slide right onto the Buffer Tube Assembly after you’ve installed it.  Each stock will have it’s own instructions, so be sure to pay attention how to install it.  Also, it is important to make sure that your stock matches the specifications of your buffer tube.  Check out the Mil-Spec vs. Commercial-Spec post for specific details on the difference. Stocks vary in all shapes, colors, and sizes… I’ve seen prices range from $50 to $250.