Exploring 80% Lowers: The Ultimate DIY Firearm Build

For gun enthusiasts, building a custom firearm can be one of the most rewarding projects. With the rise of 80% lowers, more individuals are taking the plunge into the world of DIY firearm building. Whether you are looking to build your own AR-15 or other types of firearms,  80% lowers provide the perfect starting point for a customized gun. However, completing an 80% lower requires an understanding of the process, the tools, and the legal considerations involved. In this guide, we will explore everything you need to know about 80% lowers, from their definition to the completion process, and the legal aspects of building your own firearm.

What is an 80% Lower?

An 80% lower is a component used in firearm construction, most commonly in AR-15-style rifles. The term “80%” refers to the fact that the lower receiver is 80% complete when purchased. The remaining 20% of work, such as drilling pin holes and milling the fire control pocket, must be completed by the buyer before the component can be used as a functional firearm receiver.

Because the 80% lower is not fully functional, it is not classified as a firearm by the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) until it is completed. This means it does not require a background check, serial number, or any paperwork to purchase. The 80% lower is a legal gray area, offering individuals the ability to assemble a firearm without undergoing the same regulations as a fully assembled firearm.

Why Are 80% Lowers Popular?

1. Customization Opportunities

One of the biggest attractions of building a firearm from an 80% lower is the ability to customize every aspect of the build. When you purchase a fully assembled firearm, you are limited to the factory specifications. With an 80% lower, you can choose every component, including the trigger, stock, grip, and barrel. This level of customization ensures that your firearm fits your specific preferences and needs.

The freedom to select high-quality parts allows you to create a firearm that suits your exact desires, whether you are building it for hunting, home defense, target shooting, or as a collector’s item. You can optimize the weapon’s ergonomics, aesthetics, and performance.

2. Learning Experience

For many firearm enthusiasts, the process of finishing an 80% lower and building a custom firearm can be a valuable learning experience. You will gain hands-on knowledge about the mechanics of a firearm, including how its different parts function together.

By completing the 80% lower yourself, you learn about the assembly process, the operation of the fire control group, and how different components affect the firearm’s overall performance. This knowledge is beneficial not only for building firearms in the future but also for maintaining and troubleshooting them.

3. Cost Savings

Building a firearm from an 80% lower can also save you money in comparison to purchasing a fully assembled firearm. While you will need to purchase tools and parts individually, the total cost of building your own firearm can often be lower than buying a pre-made one. You can also select components that fit your budget, eliminating the premium markup applied to factory-assembled guns.

Additionally, many tools required for building 80% lowers can be reused for future projects, making them a good investment for enthusiasts who plan on building more firearms over time.

4. Privacy

One of the most attractive benefits of using 80% lowers is the privacy it affords. Since the lower receiver is not classified as a firearm until it is fully completed, purchasing an 80% lower does not require a background check or any type of registration. This appeals to individuals who prefer to keep their firearm ownership private.

However, it’s important to note that once the firearm is completed, it is subject to all relevant firearm laws, including background checks, registration, and serializing the firearm in many states.

How Do You Complete an 80% Lower?

Completing an 80% lower requires some tools and skill, but the process is accessible to most DIY enthusiasts. The goal is to finish the remaining 20% of machining to make the receiver functional. Here’s a breakdown of the process:

1. Gather the Necessary Tools

Before starting, make sure you have the necessary tools to finish the lower receiver. These typically include:

• Drill press or milling machine: A drill press is essential for drilling holes in the receiver, while a milling machine is required for cutting the fire control pocket (the area where the trigger and other components will be placed).
• 80% lower jig: The jig holds the lower receiver in place while you work on it. It ensures that the holes and cuts are made in the correct locations.
• Drill bits and end mills: These tools are needed for drilling pin holes and cutting the fire control pocket.
• Clamps, safety glasses, and gloves: Always wear safety equipment when working with power tools.

2. Secure the 80% Lower in the Jig

The first step in the process is to clamp the unfinished 80% lower securely in the jig. The jig will guide you in drilling holes and milling the fire control pocket, ensuring the precision of the work. Make sure the lower receiver is positioned correctly before beginning.

3. Drill the Pin Holes

The next step is to drill the necessary pin holes for the trigger, hammer, and safety components. These holes need to be drilled precisely in order to ensure proper fit and function of the parts. The jig will help you line up the holes and provide a guide for the drill bits.

4. Mill the Fire Control Pocket

The fire control pocket is one of the most critical parts of the lower receiver. Milling this pocket involves removing material from the lower receiver to create space for the trigger mechanism. This step is essential for ensuring that the firearm will function properly. Depending on the precision of your tools, this step may take some time.

5. Finish the Lower

After drilling the holes and milling the fire control pocket, you will need to finish the lower by removing any rough edges. Clean the lower and ensure that the holes are deburred so that all parts fit smoothly.

At this point, you can apply a protective coating, such as anodizing or Cerakote, to protect the lower receiver from corrosion and wear.

6. Assemble the Firearm

Once the 80% lower is completed, the next step is to assemble the rest of the firearm. This involves installing parts such as the trigger, stock, buffer tube, and barrel. The assembly process will depend on the specific type of firearm you are building, but there are plenty of guides available to help you through the process.

After assembly, conduct a function check to ensure that everything works properly and that the firearm is safe to operate.

Legal Considerations When Building a Firearm

While building a firearm from an 80% lower may seem like an easy and private process, it’s important to consider the legal aspects involved. Although 80% lowers are not considered firearms by the ATF, they become regulated once they are fully completed. Here are the key legal considerations:

1. Federal Laws

Under the Gun Control Act (GCA) and the National Firearms Act (NFA), a firearm is defined as any weapon that is capable of expelling a projectile by the action of an explosive. An 80% lower is not considered a firearm until it is completed. However, once you complete the lower and assemble it into a functioning firearm, it is subject to all federal laws, including registration and serializing the firearm in some cases.

2. State Laws

State laws regarding 80% lowers vary widely. Some states, such as California, New York, and New Jersey, have stricter regulations regarding the purchase, sale, and completion of 80% lowers. In some states, it may be necessary to register your completed firearm, while in others, there are no such requirements.

In California, for example, 80% lowers are classified as “ghost guns” and require serial numbers and registration once completed. Be sure to research the specific regulations in your state before beginning the build process.

3. Serializing and Registering the Firearm

Once you complete the 80% lower and assemble the firearm, you are required to serialize the weapon in most states. Serializing a firearm involves engraving or stamping a unique number onto the lower receiver, which helps law enforcement track the firearm if it is lost or stolen.

In states that require it, you may also need to register the firearm with the appropriate authorities. Even if your state does not require registration, it may be a good idea to keep detailed records of your completed firearm for insurance or legal purposes.

Conclusion

Building a firearm from an 80% lower offers many benefits, including the ability to customize your weapon, learn valuable skills, and save money. However, the process requires careful attention to detail and the proper tools. Additionally, there are legal responsibilities involved, particularly when it comes to federal and state firearm laws. By understanding the process and adhering to the legal requirements, you can enjoy the rewarding experience of building your own firearm while ensuring that you comply with all relevant regulations.