Once you have decided that you want to get into building your own AR, you will then be presented with a huge number of questions about what you want the final form to be, and how you should go about building it.
If you are going to build from scratch, you need to start right at the very heart of the rifle, and the lower receiver. Building from this start point also then creates more questions, particularly if you are going to go the whole way and start off with an 80% lower and make a gun that is really yours from the ground up. An 80% lower receiver is, as it name implies, only completed to an 80% standard, meaning that you have to finish off the remaining 20%, and that is going to require specialist tooling.
You could try marking out and drilling/milling by hand, but you are really setting yourself up for a fall, and potentially a lot of scrap parts. No, to do it right, you need to be using well-designed jig, but that then raises more questions. The original jigs for completing 80% lowers were mostly for individual operation that you might undertake when completing the other 20%, but these have started to evolve to become more complicated and can now be used to finish all the jobs on an 80% lower.
If you want to complete a proper job on your 80% lower – and trust me, you do – then using a jig is mandatory. You just cannot hope to get all the features in the right place without one. The accuracy of your resulting weapon will be driven by the accuracy of your construction, so get a jig and use it properly. That said, there are two jigs that you ill probably want to use:
The drill-press jig
This jig is the more commonly known as the 80% lower receiver jig, and is the main one to finish a lower receiver. The jig is capable of guiding a builder to drill up to forty-two different holes that impact on your lower receiver, though you may not need them all. The drill press jig starts you off by using a smaller drill bit, like a ⅛” bit, then gradually working up to a larger ⅜” bit where needed. Drilling into the lower receiver results in you eventually carving out the fire control pocket. You will then be able to add your lower parts kit. There are many options for 80 percent lower receiver jigs. Most of these will get the job done, but they can vary significantly in quality, durability, and pricing so make sur that you shop around and choose the best you can afford. Also consider that, once you have built your first AR, you are likely to get the bug and start building more, so you will need a good, reliable jig.
The router-based jig
This is the less common of the two jigs but considered superior by some builders. The router jig differs from the drill press jig in that it requires two types of machining, with less drilling required. The router jig is used to rate only ten holes and a handheld router – something that you will need with both jigs – is used for each of the previously drilled holes. With another 6-11 different passes needed to finish the trigger pocket area this jig is pretty essential too. These jigs are generally more expensive, but their strength, durability, and speed make them a popular option despite the price. It is always very worthwhile getting one, especially if you become a serious AR customizer.
Invest in jigs and start making your AR 80% lower receiver building both accurate and speedy.