An 80 lower receiver is a great way for firearm enthusiasts to build a custom rifle while maintaining control over the manufacturing process. However, completing an 80 lower requires precision, patience, and, most importantly the right tools. Many beginners make mistakes that can compromise the functionality and legality of their build. Here are some of the most common mistakes to avoid when finishing your lower.

1. Using the Wrong Tools

One of the biggest mistakes is using subpar or incorrect tools. An lower requires specialized tools (but nothing crazy enough that it can’t be found at a local hardware store) like a drill press, router jig, and quality drill bits. We advise against using a hand drill or cheap tools because they can result in uneven cuts and a defective lower. Invest in high-quality tools to ensure clean and precise milling. However, we have seen individuals make some at-home jigs and drill presses using hand-held tools. Basically, use them at your own risk!

2. Failing to Follow Milling Best Practices

Each 80% lower receiver has guidelines into how they should be built. Ignoring guidelines can lead to misaligned holes, improper depths, or an unusable lower. Legally, American Made Tactical cannot provide those instructions.

3. Rushing the Milling Process

DON’T RUSH! Patience is key when completing a lower build. You just spent all this money on a lower for your custom build, take your time! Rushing the milling process can cause mistakes like excessive material removal, jagged cuts, or even breaking the receiver. Work slowly, take light passes, and frequently check your progress to avoid costly errors.

4. Not Securing the Lower Properly

A loosely secured 80 lower can shift during milling, leading to misaligned trigger and pin holes. Always use a quality jig and ensure the lower is clamped securely before beginning any drilling or milling.

5. Drilling Too Deep or Too Shallow

Incorrect drilling depth is a common mistake that can make your lower unusable. Many 80 lower receiver jigs have depth guides, but measuring multiple times before drilling is essential. An improperly drilled fire control cavity can lead to malfunctions or safety issues.

6. Skipping the Deburring Process

After milling, rough edges and burrs can interfere with the functionality of your lower. Skipping the deburring process can cause parts to fit poorly or create excess friction. Use fine sandpaper or a deburring tool to smooth out all edges for a professional finish.

7. Failing to Check State and Federal Laws

While completing an 80% lower is legal under federal law, some states have imposed restrictions. Before starting your build, check local regulations to ensure compliance. Some states require serialization or prohibit possession of unfinished receivers altogether. These laws change frequently, so check often!

8. Improper Assembly of Lower Parts Kit

Once your 80 lower is milled, assembling the lower parts kit correctly is crucial. Misplacing springs, incorrectly installing the trigger group, or forcing parts can cause functionality issues. Follow a detailed assembly guide and double-check each step to ensure proper function.

9. Ignoring Proper Lubrication and Maintenance

After completing your 80% lower receiver, regular lubrication and maintenance are essential. Failure to lubricate moving parts can lead to premature wear or operational issues. Keep your lower clean, inspect for any imperfections, and apply the appropriate lubricants to moving components.

Conclusion

Finishing an 80 lower is a rewarding project, and can be incredibly fun to do as a family project or with your buddies in the garage over a few cold beers, but avoiding common mistakes is crucial for a successful build. By using the right tools, following instructions, and taking your time, you can complete your 80% lower receiver correctly and legally. Always stay informed about firearm regulations and ensure every step of the process is done with precision and care.

By avoiding these mistakes, you’ll set yourself up for a smooth and successful 80 lower completion. If you’re looking for high-quality 80% lowers and milling kits, be sure to check out our full assortment of 80 lowers!