The 80 Lower Receiver: A Comprehensive Guide to Building Your Own AR


In the world of firearms, there is a growing trend among enthusiasts to construct their own weapons, primarily for personal use or as a hobby. One of the most popular components in this DIY trend is the 80 lower receiver. This guide aims to shed light on what 80 lowers are, how they are different from traditional firearms components, and why they have gained so much popularity. We’ll also touch on legal considerations and what to look for when purchasing your 80% lowers.

What is an 80 Lower Receiver?

The term 80 lower receiver refers to a partially finished firearm component that is about 80% complete. Unlike a 100% lower receiver, an 80 percent lower isn’t considered a firearm by the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) until you, the end user, complete the remaining 20% of the machining work. This makes 80 lowers an attractive option for gun enthusiasts who wish to build their own AR-style rifles or pistols.

Types of 80% Lowers

  • AR-15 80% Lowers: For the popular AR-15 model
  • AR-10 80% Lowers: For AR-10 rifles, which are typically chambered for larger rounds
  • 9mm 80% Lowers: For building 9mm caliber firearms
  • 80 AR Lower in Polymer: Made of polymer material, they are easier to machine but less durable
  • 80 AR Lower in Aluminum: Made from aluminum, these are more durable but require more sophisticated tools

Benefits of Using 80 Lower Receivers

  • Customization: You can customize an 80 lower receiver to fit your exact specifications, something that’s not always possible with off-the-shelf options.
  • Privacy: 80% lowers can be purchased without the need for a federal firearms license (FFL), allowing you more privacy.
  • Educational: The process of completing an 80 ar lower teaches you about the mechanics and functioning of firearms.

Legal Considerations

It is crucial to note that while 80% lowers are not classified as firearms, the moment you complete the machining process, it becomes a firearm in the eyes of the law. Therefore, you must comply with all federal, state, and local laws concerning firearms ownership.

What to Look for When Purchasing 80 Lower Receivers

  • Material: Choose between polymer and aluminum based on your needs and skills.
  • Compatibility: Make sure the 80 lower receiver is compatible with the other components you plan to use.
  • Brand Reputation: Look for brands that are known for quality and reliability.

How to Complete an 80 Percent Lower

Completing an 80 percent lower requires some expertise in machining and a set of specialized tools. You’ll need:

  • A milling machine or a drill press
  • Various drill bits and end mills
  • A vise to hold the lower securely

After getting the required tools, you can proceed to drill holes and remove material as specified in the instructions that come with your 80% lower.


The 80 lower receiver offers an opportunity for firearms enthusiasts to build a custom AR-style weapon, either for personal use or as an educational project. Despite the legal considerations that come with completing an 80 ar lower, many find the process rewarding and engaging. If you’re considering taking the plunge, make sure to do your research, comply with all legal obligations, and choose a quality 80% lower to start your project.

Jane Tudor

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