Complete Guide to 80% Lowers - Legality, Build Process, Tips

The Complete Guide to 80% Lower Receivers

80 percent lowers, sometimes called 80% lowers, are partially completed lower receivers that are not considered firearms. They provide a starting point for building a custom rifle but require additional machining and parts to make them functional.

Building on an 80% lower provides flexibility compared to buying a complete lower receiver. Read on to learn what 80% lowers are, the legality issues, how to complete them, and tips for your custom rifle build.

What Are 80 Percent Lowers?

80% lowers are partially manufactured lower receivers that are not classified as firearms by the ATF. They require an additional 20% or more of machining by the end user to become functional.

A lower receiver is the part of the rifle that houses the trigger mechanism and magazine well. It is legally considered the firearm itself according to US gun laws.

By remaining in an incomplete state, 80% lowers can be sold without background checks or compliance with federal firearms regulations.

Why Use an 80 Percent Lower?

There are several advantages to building a rifle from an 80% lower versus buying a complete lower:

• Avoids firearm registration since it is not a gun when sold
• Bypasses background checks required for complete lowers
• Lower cost than buying a finished lower
• Allows complete customization of the build

The DIY appeal and freedom from regulatory constraints make 80% lowers a popular choice among firearms hobbyists and preppers.

Legality and Regulations

While unregulated at the federal level, some states prohibit or restrict 80% lowers. State and local laws may require registration, serialization, and background checks on self-made firearms.

It is the responsibility of the end user to understand all applicable laws before manufacturing a firearm from an 80% lower. Misuse could result in criminal charges.

How to Complete an 80 Percent Lower Receiver

While not extremely complex, finishing an 80% lower takes precision, patience, and the right tools. Here is an overview of the machining process:

Understand the Steps Involved

Completing an 80% lower involves the following sequential steps:

1. Fire control group cavity
2. Trigger slot
3. Trigger pinholes
4. Hammer pinhole
5. Safety selector switch hole
6. Magazine catch and release holes
7. Rear takedown pin hole
8. Buffer detent hole
9. Trigger guard holes
10. Final drilling and milling

Each step must be precision aligned with those prior. Rushed or sloppy work can ruin the lower. Guidance from an experienced builder is extremely helpful.

Acquire the Right Tools

Finishing an 80% lower requires a drill press and jig kit at minimum. A router jig allows completing the fire control group cavity efficiently.

You'll also need quality drill bits, end mills, safety equipment like goggles and gloves, vises, and a Dremel tool.

Purchase a jig designed specifically for your lower model for proper alignment. Invest in suitable drill bits for metalwork.

Prepare Your Workspace

Completing a lower generates a lot of metal shavings and debris. Set up your workspace accordingly:

• Clean, level, and well-lit surface
• Vacuum nearby to manage debris
• Securely mount drill press and vise
• Nearby access to a workbench and vice
• Safety equipment and fire extinguisher

Preparation prevents errors and allows you to work efficiently and safely.

Follow Plans and Instructions

Closely follow all instructions provided with your jig kit and 80% lower. Measure twice before drilling to avoid mistakes.

Work slowly and patiently, especially when using the router jig. Rushing through steps risks ruining the lower.

Having an experienced builder guide you through the process in person is ideal if possible.

Tips for Completing Your Custom Build

The possibilities are nearly endless when building your own custom rifle from an 80% lower. Keep these tips in mind to execute your vision:

Research Compatible Parts

Not all AR-15 parts work seamlessly together. Research meticulously to ensure all components are compatible.

Pay special attention to the lower parts kit, buffer tube assembly, upper receiver, barrel, and handguard selections.

Roughen Surfaces for Paint Prep

If painting your completed lower, roughen the surface slightly with 120 grit sandpaper first. Remove any oils or residue with brake cleaner before primer.

A properly prepped surface allows paint to adhere better for a long lasting finish.

Consider a Two-Stage Trigger

A single stage trigger works fine for most civilians. But a two-stage trigger provides a smoother, lighter trigger pull.

They work well for precision shooting. Just ensure it's compatible with your lower and trigger setup.

Upgrade Key Components

While not always essential, aftermarket parts can enhance performance and functionality. Consider upgrades like:

• Ambidextrous safety selector
• Extended magazine or bolt release
• Anti-walk trigger pins
• Enhanced pistol grip
• Adjustable buttstock

Upgrades provide ergonomic and functional enhancements to suit your preferences.

Mind Usage and Legal Guidelines

Ensure you follow both federal and state laws when using a homebuilt firearm. Some states prohibit certain modifications like high capacity magazines.

Improper usage could result in criminal charges. Always use your rifle legally and responsibly.

Frequently Asked Questions About 80% Lowers

For those new to the world of 80% lowers, questions remain. Here are answers to some of the key questions.

Are 80% Lowers Legal?

Federally, 80% lowers are legal and unregulated in most states. However, state laws vary significantly. Research your state's laws thoroughly before purchasing or manufacturing.

Can an 80% Lower Become Full Auto?

No, converting an 80% lower or any semi-automatic rifle into full auto is illegal under the NFA. Modifying the fire control group this way could result in felony charges.

Do 80% Lowers Require a Serial Number?

Federally, 80% lowers do not require a serial number since they are not firearms initially. However, some states require applying a serial number to home built firearms.

Are Jig Kits Universal?

No, 80% lower jig kits are designed for specific lower models like the AR-15 or AR-10. Ensure the jig matches your lower model exactly before purchasing.

Can a Felon Build an 80% Lower?

No, federal law prohibits felons from possessing firearms, including building them from 80% lowers. Violating this law could mean felony charges.

Build Your Dream Rifle From an 80% Lower

With proper skills and diligence, an 80% lower provides the foundation for building your ideal custom rifle. Just ensure your build complies with all applicable laws.

With the right know-how and tools, you can avoid regulations and build the firearm you want from the ground up. The end result will be a rifle you crafted yourself from an 80% lower.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult with a healthcare professional before starting any new treatment regimen.