What is an 80% Lower?

If you are a firearm enthusiast with an interest in building your own gun, you may have heard of the 80% lower, 80 lower, receiver blanks, or unfinished receiver. This incomplete firearm frame provides the buyer with an unfinished lower receiver. Basically, this receiver is 80 percent complete, and the person who makes the purchase completes the other 20 percent at home. That entails some drilling and cutting of the frame to prepare it for the other components.

Popular 80 lower receivers to complete include the AR-15, AR-10, and Glock pistols. These are available in forged, billet, and polymer options. Polymer 80% lowers are the easiest to complete at home. These receivers are incredibly light, and they come with their own jig. The softer material does not require anything more than a common drill press to complete the manufacturing. However, they are not as strong, and they are more prone to scratches and imperfections.

The process does not require a high degree of technical ability but depending on the type of firearm you will likely need to drill the hammer pin, trigger pin, and safety selector lever holes as well as cut the fire control cavity. After finishing the additional steps to prepare your receiver, you will add the components from a lower receiver parts kit.

Tools Needed to Complete an 80 Lower

It is essential that you use the appropriate tools to complete your project. If you are not careful when you drill your receiver you may create irreversible flaws and end up with a weapon that does not fire. To achieve clean cuts and drill precise holes, it is recommended you have the following tools:

Drill press or handheld drill
80% jig with bits
Machining oil
Bench vise
Canned air
Gloves
Eye protection

Pros to Purchasing an 80% Lower

Since the unfinished receiver is not functional without additional fabrication at home, it cannot be defined as a firearm. That means you can purchase and build your gun without a Federal Firearms License (FFL). These guns do not require a serial number and there is no background check. Purchasing a completed firearm requires a firearm transaction record, but the 80% lower receiver can ship directly to your home with no need to fill out forms or complete the purchase through a gun dealer.

Completing the fabrication at home can also be more affordable, but this depends largely on whether or not you already possess the required tools to complete the project. It also depends on how much customization you are seeking and what types of additional options you choose. Many gun enthusiasts choose to purchase an 80 lower simply because they want a customized firearm and enjoy learning about the process required to manufacture their rifles or pistols.

The Law and the 80% Lower

The Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) does not consider receiver blanks to be firearms because they are sold without machined fire control cavities. That means they are not regulated under the Gun Control Act. However, there are a few states that disagree with this, and they have restricted or banned the sale of 80% lowers. Laws change, so it is important to check with your own state to confirm the legality of purchasing an 80 lower, but the following states have placed some restrictions on blank receivers at one time: