The allure of crafting your own firearm has attracted countless gun enthusiasts, hobbyists, and even skeptics. The cornerstone of this do-it-yourself endeavor is the 80 lower receiver. Unlike complete receivers, 80% lowers give you the freedom to finish the remaining 20% of the product, offering unparalleled customization options. In this guide, we explore what an 80 lower receiver is, why it’s the go-to choice for DIY firearm builds, and what you should consider when diving into this project.

What Exactly Is an 80 Lower Receiver?

An 80 lower receiver refers to a firearm component that is 80% completed. These unfinished receivers lack certain features that would categorize them as a firearm according to federal law. This means you can purchase an 80 percent lower without undergoing the standard background checks, but once you complete the remaining 20%, you’ll be the proud owner of a fully functioning firearm (and all legal responsibilities that come with it).

Types of 80 Lower Receivers

  • AR-15 80 Lowers: Ideal for building AR-15 style rifles, the most popular type of rifle in the U.S.
  • AR-9 80 Lowers: Geared towards those interested in a smaller, pistol-caliber carbine.
  • AR-10 80 Lowers: Suitable for those looking for more firepower and are willing to handle a larger, more powerful round.
    Advantages of Using an 80% Lower
  • Customization: One of the most appealing aspects of 80 lowers is the ability to make a weapon tailored to your specific desires.
  • No FFL Required: Purchasing an 80 lower receiver does not require an FFL (Federal Firearms License), making the process simpler and more private.
  • Skill Building: Completing an 80 ar lower is a hands-on project that hones your mechanical skills.

Legal Aspects to Consider

Even though an 80% lower isn’t considered a firearm by law, as soon as you complete the required machining, it will be. Therefore, you must be aware of and comply with all state and federal laws, which may include registration or specific prohibitions.

  • Buying Guide: What to Look for in an 80 Lower Receiver
  • Material: While aluminum is more robust, polymer 80 lowers are easier to machine.
  • Fit and Compatibility: Always ensure the 80 lower receiver will fit with the other parts you plan to use.
  • Reputation: Opt for trusted brands known for their quality 80% lowers.
  • User Reviews: Reading reviews from others who have completed their 80 ar lower can provide invaluable insights.

The Process of Completing an 80 Percent Lower

  • You will need some specialized tools and safety gear to complete an 80 percent lower. The primary tools include:
  • Milling machine or quality drill press
  • Drill bits and end mills
  • Vise and/or jig for stabilization

Follow all safety protocols and guidelines, ensuring you measure and mill carefully. This is crucial for the safety and functionality of your final product.


80 lower receivers offer a unique entry point into the world of custom firearms. While they do require a level of mechanical skill and understanding of legal obligations, the rewards are well worth the effort. Whether you’re a seasoned gunsmith or a curious beginner, 80 lowers provide an excellent opportunity to develop your skills while building a one-of-a-kind firearm.