Introduction
The allure of building your own firearm is undeniable. For many enthusiasts, the journey begins with an eighty percent lower receiver. Unlike a completed lower, this partially machined component offers a unique opportunity to learn about firearm construction and customize your build. This guide provides a detailed, step-by-step approach to finishing an eighty percent lower, empowering you to complete this exciting project with confidence. However, it’s essential to understand the legal landscape before you begin. Building a firearm is subject to specific regulations, and ignorance is not a defense. This article is for informational purposes only and is NOT legal advice. Always consult with legal professionals and familiarize yourself with all applicable local, state, and federal laws before proceeding. We’ll also cover the required tools and safety gear to ensure you can complete your build safely and successfully.
Understanding Eighty Percent Lowers and Legal Considerations
What exactly is an eighty percent lower receiver? It’s a partially complete lower receiver. The eighty percent designation means the component is unfinished, leaving the critical internal machining to the builder. These lowers are often referred to as “blanks” or “raw” receivers. The term “firearm” is a legal term, and its definition can vary. Generally, a firearm is an assembled weapon designed to expel a projectile by the action of an explosive. A “receiver” is the primary component, the main housing for the firearm. An eighty percent lower is *not* considered a firearm under federal law, as it requires further machining to function. This is a key distinction, but be aware that some state and local laws may differ.
Legal Compliance – A Mandatory Responsibility
Navigating the legal landscape is crucial. This article is for informational purposes ONLY. The author and publisher of this material are not responsible for the individual’s actions. The user is *solely* responsible for researching, understanding, and complying with ALL applicable laws and regulations pertaining to firearms, eighty percent lowers, and homemade firearms. The laws regarding firearm ownership, manufacture, and modification vary significantly by jurisdiction.
Federal Regulations
While eighty percent lowers are currently not considered firearms under federal law, this can change. The Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) is the federal agency responsible for regulating firearms. Always refer to the ATF’s website and publications for current regulations.
State and Local Laws
State and local laws can be more restrictive than federal laws. Some states require registration, background checks, or have restrictions on the types of firearms that can be legally owned. Some cities and municipalities also have their own regulations.
Definition of Manufacturing
Be aware of the legal definition of “manufacturing” a firearm, as this activity may be subject to specific regulations.
It is *imperative* that you conduct thorough research and consult with legal professionals or local law enforcement if you have any questions or uncertainties about the laws in your area. Failure to comply with firearm laws can result in severe legal penalties. Always prioritize your legal obligations.
Safety First: Your Wellbeing is Paramount
Working with power tools and metal can be hazardous. Always prioritize safety. Before starting, gather your personal protective equipment (PPE) and familiarize yourself with your workspace.
Personal Protective Equipment (PPE)
- Safety Glasses/Goggles: Always wear safety glasses or goggles to protect your eyes from flying debris.
- Gloves: Gloves provide a secure grip, protect your hands from abrasions, and keep your hands clean.
- Ear Protection: Milling can produce loud noises. Wear earplugs or earmuffs to protect your hearing.
- Face Mask/Respirator (Optional): If you’re working in an area that generates dust, wear a dust mask or a respirator with appropriate filtration.
Workshop Safety
- Well-lit and Ventilated Work Area: Ensure your workspace is well-lit to see your work clearly and properly ventilated to remove metal shavings and fumes.
- Clear Workspace: Keep your work area clear of clutter and obstructions to prevent accidents.
- Secure Clamping: Always securely clamp the eighty percent lower in your jig to prevent movement during the machining process.
- Proper Tool Handling: Use tools correctly and handle them with care. Be aware of the dangers associated with sharp edges, spinning blades, and moving parts.
- Emergency Preparedness: Know the location of your first aid kit and have a plan in case of an emergency.
Tools and Materials You Will Need
Successfully finishing an eighty percent lower requires the right tools and materials. This isn’t an exhaustive list, but it provides a solid foundation.
The Eighty Percent Lower Receiver
A key consideration is the type of receiver. The most common is for the AR-15 platform, but you can also find them for AR-10 and other firearms. The material can be important. Aluminum is generally easier to machine. Steel lowers offer increased durability, but may be more challenging to finish. Select the material that aligns with your experience and budget.
Jig
A jig is a critical component that aligns the eighty percent lower and guides your tools. There are various types of jigs available. Universal jigs can accommodate different lowers. Dedicated jigs are designed for specific lower models. Some jigs include end mills. A good jig is essential for accurate machining. Research and choose a jig with clear instructions and positive reviews. Consider the material of the jig.
Milling Machine or Router
These machines remove material to create the fire control group pocket and other features. A small, dedicated milling machine is generally preferred for its precision and control. A router can also be used, particularly with certain jig designs.
End Mills/Drill Bits
These are the cutting tools used to remove material. You’ll need a variety of sizes for different operations. High-speed steel end mills are a good starting point, but carbide end mills offer greater durability and are recommended for harder materials. Research the appropriate end mill type and size needed for each step. Purchase a set with multiple sizes to cover various drilling and milling tasks.
Drill Press
A drill press is highly recommended for drilling holes. It provides accuracy and control that are difficult to achieve with a handheld drill.
Other Tools
- Drill press vise: If using a drill press, a drill press vise is essential for securely holding the receiver.
- Hand drill (as a backup): A hand drill can be useful for smaller tasks or as a backup.
- Vice: A bench vise is invaluable for holding parts securely during various operations.
- Center punch: Used to mark the starting points for drilling.
- Measuring tools: Calipers and rulers are required to measure and verify dimensions.
- Lubricant/Cutting fluid: Reduces friction and heat during machining, extending tool life and improving the finish.
- Deburring tool: Removes sharp edges and burrs after machining.
- File: For minor adjustments and deburring.
- Hex keys/Allen wrenches: Necessary for tightening and loosening screws.
- Cleaning supplies: For cleaning the lower after each step.
- Parts to be used: You’ll need to gather the rest of the parts.
The Finishing Process: A Practical Guide
The finishing process is where you transform the raw eighty percent lower into a functioning component. Before beginning, carefully review the manufacturer’s instructions for your specific jig and lower.
Preparation
- Securely mount the eighty percent lower in your jig. Make sure the lower is firmly clamped to prevent movement during milling or drilling.
- Review the included instructions, even if you’ve completed the process before.
- Familiarize yourself with the jig.
Drilling the Trigger Pocket (or Equivalent)
This is often the first major operation. Carefully center the drill bit on the marked location for the trigger pocket. Choose the correct drill bit size according to the specifications in the instructions. Use lubricant generously. Drill slowly and steadily, removing material in small increments. The instructions provide specific depth measurements for the drill bits. Maintain precise control over the depth.
Drilling the Pin Holes
Drill holes for the trigger, hammer, and safety selector. Carefully center the drill bit and ensure that the holes are perpendicular to the surface. Drill slowly, applying constant pressure. Use a small amount of lubricant. The critical aspect here is accurate alignment.
Cutting the Fire Control Group (FCG) Pocket
If using a milling machine, use the appropriate end mill to mill out the trigger pocket. Make sure your machine settings are correct and you use lubricant. Take multiple passes, removing a small amount of material each time to achieve the correct dimensions. Follow the instructions for your jig and lower.
Removing Material for the Bolt Catch (if applicable)
If needed, use the appropriate end mill or drill bit to remove material for the bolt catch. Measure the pocket dimensions using calipers.
Deburring and Finishing
After machining, the lower receiver will have sharp edges and burrs. Use a deburring tool to remove these, taking care not to damage the metal. File edges to refine them. Thoroughly clean the lower receiver with a degreaser and solvent to remove any metal shavings and cutting fluid.
Testing and Troubleshooting
Once the machining is complete, it is essential to test the fit of the components and address any issues.
Test Fitting Components
Install the fire control group, safety selector, bolt catch, and other components. Check for smooth operation of all moving parts. Test the trigger pull, safety, and bolt catch release.
Troubleshooting Common Issues
- Loose or Tight Parts: If a part is loose, consider a slightly larger pin or a shim. If it’s too tight, you can gently file or hone the part.
- Trigger Malfunctions: If the trigger doesn’t function, recheck the installation and dimensions. Ensure the trigger and hammer are compatible.
- Difficulties with Pin Installation: If pins are difficult to install, you may need to ream the holes slightly. Use the correct size reamer.
- Burrs or Sharp Edges: Ensure that all burrs have been removed and the finish has been applied, as needed.
Adjustments and Corrections
Carefully address any issues.
Post-Finishing Considerations
Once the eighty percent lower has been successfully machined and the parts fit, you can consider some finishing options.
Surface Finishing (Optional)
- Anodizing: A chemical process that creates a protective and aesthetically pleasing finish.
- Cerakote: A ceramic-based coating that provides excellent durability, corrosion resistance, and customization options.
- Painting: A more basic option that allows for custom colors.
Consult with professionals or follow online tutorials for surface finishing techniques.
Assembly
Once the lower is machined and finished, assemble the complete lower receiver using the AR-15 parts (if applicable). Torque the screws and parts to the specified manufacturers’ recommendations. Refer to the manufacturer’s specifications for proper assembly.
Conclusion
Finishing an eighty percent lower is a rewarding project that can enhance your understanding of firearms. This guide provides a comprehensive overview of the steps involved, from understanding the legal landscape to machining and final assembly. Always prioritize safety, follow the instructions carefully, and research your local, state, and federal laws.
Responsible firearm ownership includes adhering to the law, knowing safe gun handling practices, and proper storage. Take your time, be patient, and enjoy the process.
Remember, this article is a guide to finishing an eighty percent lower receiver, but building and owning a firearm is subject to legal requirements. As always, consult with legal professionals and comply with all applicable laws.
