Posted by 80-Lower on Feb 6th 2019


So, you’re ready to build your first 80% lower. It may seem like a daunting task, putting machine to metal, but we’re here to reassure you – and give you some critical tips! These recommendations will help make the difference between a fun learning experience and a proud, home-built firearm, and potential failure. Here are secrets you should know before finishing an 80 lower!

#1: Know how to finish your 80% lower confidently, first

Most of us aren’t machinists and most of us have never had the opportunity to understand even basic metalworking. Because of this, knowing the fundamentals of this project by heart before attempting it is the only way to ensure success.

Watch the complete 80% lower tutorial included with your jig, first. Read through the instructions and understand each measurement. Know how to make the necessary adjustments to your drill bits and end mill bit. And most importantly, understand how your finished AR-15 lower receiver will be used to house your trigger assembly and internals.

Knowing these steps before you try to follow along will ensure you’re only making mechanical decisions – not trying to understand the fundamentals and making mistakes while doing so.

#2: Stick with the recommended handheld router

We know, we know – if you’re into building an 80% lower, chances are you’re already interested in building things with your hands. Maybe you have a handheld router at home – maybe you’ve used it once or twice for woodworking.

Unless you’re a pro at tooling and milling, stick with the recommended handheld router when it comes time to build your 80% Lower. Most 80% jigs on the 80% lower market have been designed and tested using the Porter Cable 6430 Laminate Router (and most tooling and tutorials are set up for this router).

The Porter Cable wasn’t just chosen for 80% lower work by chance – it has all the features you want, and just the right amount of power and tech for consistent metal work.

#3: First time? “Recommended” tools are required

This one may be more of an opinion than a top tip or secret, but we feel it’s the only way to have fun with this project (instead of worrying about failing): Get the recommended tools. That means investing in the following:

  •         AR-15 Build Mat
  •         AR-15 Punch Set
  •         Birchwood Casey Aluminum Black
  •         Brass Gunsmithing Hammer
  •         Drill Press Vise

#4: Investing in extra tooling is critical

Your 80% Lower Jig will come with all the necessary tooling – drill bits and an end mill bit – that you need to machine your 80% lower. Investing in just one extra set of drill bits and the appropriate end mill bit will ensure you’re not stuck if a bit snaps.

Furthermore, an extra end mill bit is strongly recommended when finishing one forged 7075 80% lower. These hardened, forged lowers are much more resistant to machining, and regardless of which lower you opt for, those extra bits will keep your project going smoothly when that likely first mistake happens.

DISCLAIMER: If you are new to the world of DIY gun building, you likely have a lot of questions and rightfully so. It’s an area that has a lot of questions that, without the correct answers, could have some serious implications. At, we are by no means providing this content on our website to serve as legal advice or legal counsel. We encourage each and every builder to perform their own research around their respective State laws as well as educating themselves on the Federal laws. When performing your own research, please be sure that you are getting your information from a reliable source.