Building Your Own Firearm: A Beginner’s Guide to 80% Lowers

For firearm enthusiasts, there’s a unique sense of satisfaction in building your own weapon from scratch. One of the most popular ways to begin is by using an 80% lower receiver. These partially completed components offer a simple, cost-effective, and customizable approach to assembling a firearm. If you’ve ever wondered how to build your own rifle or AR-15, this guide will walk you through the essentials of working with 80% lowers, including why they’re so popular, the process involved, and what you need to know to get started.

What is an 80% Lower Receiver?

An 80% lower receiver is a firearm component that’s 80% finished, with the remaining 20% left to be completed by the builder. Typically, it refers to the lower receiver of an AR-15 or AR-10, though 80% lowers exist for a variety of firearms. The term “80%” indicates that the piece isn’t fully machined and cannot function as a firearm until the builder completes the remaining steps.

Because the lower receiver is considered unfinished, it is not classified as a firearm under federal law, which allows people to purchase it without an FFL (Federal Firearms License). However, once the lower receiver is completed, it must be treated as a regular firearm according to the law.

Why Are 80% Lowers Popular?

1. Cost Savings: One of the main reasons people choose 80% lowers is cost savings. Purchasing a fully assembled lower receiver can be expensive, especially when buying high-quality parts. By using an 80% lower, you can save money while still having the opportunity to customize and create a weapon tailored to your preferences.

2. Full Customization: Building from an 80% lower gives you complete control over the final product. You can choose every part, from the handguard to the stock, ensuring that your firearm meets your exact specifications. This level of customization is highly appealing for those who want a personalized firearm or those who enjoy experimenting with different configurations.

3. Hands-On Learning Experience: For those new to firearms or gunsmithing, working with an 80% lower is an educational experience. You’ll gain hands-on knowledge of how firearms are assembled and learn to operate tools and machinery like a drill press, jigs, and possibly even CNC machines. This experience can be incredibly rewarding and help you develop valuable skills in the world of gunsmithing.

4. Privacy and Independence: Building your own firearm from an 80% lower means you don’t need to register the lower receiver or undergo a background check when purchasing it. While some may not see this as a necessity, others appreciate the privacy and sense of independence that comes with the ability to build a firearm legally without the oversight of governmental agencies.

The Legal Considerations of Building an 80% Lower

While 80% lowers are legal to purchase in many places, there are important legal factors to consider:

• Federal Law: At the federal level, 80% lowers are not considered firearms until they are fully completed. This means that the purchase of an 80% lower is not subject to the same regulations as buying a fully assembled firearm. However, once you complete the lower, it will be treated as a regular firearm and will be subject to applicable laws.
• State Laws: Different states have their own laws governing 80% lowers, and some have stricter regulations than others. States like California, New York, and New Jersey may require you to register your completed lower receiver or add a serial number to it before it can be used legally. Always check your state’s laws to ensure that you’re compliant before starting a build.
• Finishing the Lower: When you finish your 80% lower, it becomes a legally recognized firearm. Some states may require that you apply a serial number or go through additional registration processes. Always research the specific requirements in your state before completing the firearm.
• Selling or Transferring: If you decide to sell or transfer your completed firearm, you must comply with local laws. Some states may require a background check or transfer through a licensed firearms dealer.

Steps to Completing Your 80% Lower

Building your firearm from an 80% lower requires both the right tools and a bit of patience. Here’s a general overview of the steps involved:

1. Gather Your Tools: Depending on your experience and the tools available to you, you can either use basic hand tools or more advanced machinery like a CNC machine. At a minimum, you’ll need a drill press, jigs, drill bits, and files.

2. Use a Jig Kit: A jig kit is a vital part of completing an 80% lower. The jig serves as a template, guiding you to drill and mill the necessary areas with precision. These kits usually come with instructions and all the necessary components to help you finish your lower receiver accurately.

3. Machining the Fire Control Pocket: The most important part of finishing the 80% lower is machining the fire control pocket. This involves milling out the space that will house the trigger assembly. This is a delicate step that requires precision to avoid damaging the receiver or creating a malfunctioning firearm.

4. Drilling and Cutting: After completing the fire control pocket, you will need to drill holes for the pins that will hold the trigger assembly and other parts. You may also need to make cuts in other areas, such as the magwell and buffer tube. This step is critical and should be done carefully to ensure that all components fit correctly.

5. Assemble the Firearm: Once your 80% lower is fully completed, you can proceed with assembling the rest of the firearm. Attach the upper receiver, install the stock, trigger group, and other necessary parts. Finally, check the entire firearm for function before you head to the range.

Safety and Testing Your Firearm

Once you’ve completed your firearm, safety is the next step. Here’s what you should do:

• Perform a Function Check: Before firing, ensure that the trigger, safety selector, and magazine release all function correctly. Run through all the firearm’s actions to make sure that everything is working smoothly.
• Inspection by a Professional: If you’re unsure of your work, consider taking your completed firearm to a professional gunsmith for an inspection. They can verify that everything is assembled correctly and that the firearm is safe to use.
• Test Fire Safely: Always test your completed firearm in a controlled, safe environment like a shooting range. Use proper safety equipment, such as ear and eye protection, and never fire a weapon without ensuring that it is properly assembled.

The Pros and Cons of 80% Lowers

Before starting your project, it’s important to weigh the pros and cons of using an 80% lower:

Pros:

• Cost-effective compared to fully assembled lowers.
• Complete control over customization and firearm design.
• Educational and hands-on experience in firearms assembly.
• No need for background checks or registration when purchasing the lower.

Cons:

• Requires a significant time investment and access to tools.
• Legal complexities in certain states.
• Need for specialized equipment and knowledge for precision.

Conclusion: Should You Build from an 80% Lower?

Building a firearm from an 80% lower can be a highly rewarding experience for those who are willing to invest time and effort. It offers the opportunity to save money, customize your firearm, and gain valuable gunsmithing skills. However, be sure to familiarize yourself with all relevant legal considerations and ensure you have the right tools for the job.

If you’re ready to begin your next DIY project, head over to 80-Lower.com to explore a wide selection of 80% lowers and building kits.