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5 Different Techniques to Complete an 80% Lower

Owning an AR-15 is a big deal, but building one is a statement. If you’re ready to become a DIY AR-15 builder you’re about to join an elite club of other DIYers who can all take pride in their work. Whether you only plan to build one AR-15 or an entire collection, the first tool you need is awareness. There are a variety of ways to complete your 80% lower receiver. Before you get started, take a look at these five options to choose the way that is suitable for your skill level and the tools you have available.

CNC Machine

A CNC machine allows you to automate much of the process of completing your 80% lower. The machine is operated by a computer numerical control, which is why it’s typically called a CNC machine. There are two programs that control the CNC machine: computer-aided design (CAD) and computer-aided manufacturing. Each of these programs works to offer top-notch precision in the completion of 80% lower receivers.

Before you can use a CNC machine, you will want to program it with a CAD program so you can complete your order to MilSpec standards. There are a variety of CAD programs available online to get you started.

One thing to keep in mind when using CNC machines is that it requires an adequate knowledge of CAD programming knowledge as well as familiarity with operating a CNC machine. Most people don’t have access to a CNC machine, so this isn’t always the popular option amongst DIYers.

Milling Machine

Milling machines are used for both metal and wood, and are a viable option for completing your 80% lower. Some milling machines are automated while others require more manual work. Either option just about always offers precision milling capabilities along with multi-axis machining.

Unlike the CNC machine, a milling machine lends well to those with limited knowledge. The basics are easy for most people to quickly pick up with some one-on-one time from someone who is familiar with using a milling machine. Still, as simple as it is to catch on to the basics, milling machines can be slightly intimidating for first time users.

Drill Press

The drill press is likely the simplest way to complete your 80%lower receiver. It is a pedestal styled drill mounted on a stand. The tool is normally portable with a spindle and chuck that move parallel to the axis of the pedestal. The drill press is manually operated and normally allows for various settings of depths to drill or mill. In addition to the depth settings, there is also usually a clamp for you to secure the 80% lower while you drill.

One thing to keep in mind is that the drill press doesn’t provide the same level of precision that you might find with a CNC machine or a milling machine. Still, if you are not experienced with either of those machines, the drill press is the best place to start for first timers. By following the very detailed instructions for using a drill press, it will be hard to tell your lower was completed with a drill press.


A router operates on a single spindle to hollow edges and faces of solid surfaces like metal and wood. You can attach a variety of rotary tools or bits to the router to complete the job. The work is completely manual, but if you’ve got access to a router it is a decent alternative.

If you choose to use a router, you should take the utmost safety precaution. Because the router turns at a significant rate of speed, you want to be careful when using the cutting tools. It is also necessary to wear proper eyewear to protect your eyes from excess shavings and other possible mishaps. Finally, when using a router it is best to go with carbide bits that are designed for aluminum so the router doesn’t stick or melt the aluminum to the bit.

Electric Hand Drill

Electric hand drills are pretty popular as household items. Most, if not every, DIYer owns one. The tool can be fitted with a driving or drilling attachment and it is most notably used for drilling holes in wood, steel and other solid materials. This tool requires the least amount of skill and is also quite economical.

When completing your lower with a hand drill, be aware that the drill will not provide a steady axis so the level of precision rests solely on the operator. A hand drill also will not provide depth settings, which means the operator needs to follow the necessary depth without any added support.

Completing an AR-15 lower receiver is an exciting task to embark on. But before you dive right in, take some time to choose a build option that fits your tools and your skill level. Once you choose your build method, we suggest starting with an AR-15 80% Lower Jig, 2 Pack which comes with two 80% lower receivers, a lower jig and step-by-step instructions for only $199.99.



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