What You Need To Know To Build An AR-15 Lower Receiver

What You Need To Know To Build An AR-15 Lower Receiver

Building your own AR-15 lower receiver can be an incredibly rewarding experience. Not only will you get the gratification that comes with making something by yourself, but you will also open the doors to a world of customization options simply not available when buying a completed gun.

Before you begin, make sure you know the appropriate laws surrounding registry of Semi-Automatic rifles in your state. It is important to remember that buying a ready-made AR-15 lower receiver means you are effectively purchasing a firearm, and so the applicable laws apply.

If you choose to go with an 80% lower receiver you are not purchasing a firearm and do not have to register it; however you must be comfortable with (and have the equipment for) drilling and milling as the trigger pocket and holes for the safety, and hammer pins are not pre-drilled. Use of an 80% lower jig will help ensure accuracy should you go down this road. Choosing to start with an 80% Lower Receiver allows you to purchase the component online and have it delivered to your home directly instead of having to pick it up from a federally licensed dealer or deal with an FFL transfer.

Of course, before you begin you should ensure that you have all of the required tools and equipment to undertake this task.

To put together an AR-15 lower, you will need the following:


  • Punch Set
  • Rubber mallet
  • Pen knife
  • AR-15 Lower vise block and bench vise
  • Allen (Hex) key set


  • AR-15 Lower Receiver unit (pre-made or 80%)
  • Buffer tube assembly
  • Lower parts kit
  • Fire control system (Trigger and hammer assembly)
  • Stock

One cardinal rule when it comes to building an AR-15 lower is to always complete the section you’re working on before moving on to the next. This will help to avoid missing any steps that could prove disastrous later on.

Now that you’ve got your tools and equipment set up, and the stripped lower is secured into your bench vise you’re ready to start putting it together. The below is a list of steps for assembling your AR-15 Lower. Although you do not have to use this particular order, think of it as a good starting step!

  • Install the magazine catch
  • Install the trigger guard assembly
  • Install the bolt catch assembly
  • Install the trigger assembly
  • Install the safety
  • Install the takedown pin
  • Install the grip
  • Install the receiver extension
  • Install the buffer assembly and stock

Make sure you keep good track of each component whilst assembling your build. It is even a good idea to leave part in their packaging until you’re ready to install them. In all it is vital that you do not lose any small pieces, or install them in the incorrect locations. Remember that catastrophic failure of any component in a firearm can lead to serious injury or worse so it imperative that you take your time and do it right the first time.

As with anything tailor made, sometimes (but not always) it can be more expensive than just buying off the peg, but you can almost guarantee it will be a better fit for you. By building your own AR-15 Lower, the customization options are almost endless. You can spend as little or as much as you’d like on your build, the world is your oyster!

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