How to Mill an 80 Lower Receiver: A Comprehensive Guide
Milling an 80 lower receiver is a crucial step in the process of building an AR-15 rifle. This guide will walk you through the essential steps and considerations to ensure a successful and safe build. Whether you’re a beginner or an experienced gunsmith, understanding how to mill an 80 lower receiver is key to creating a custom firearm that meets your specific needs.
Understanding the 80 Lower Receiver
The 80 lower receiver is the foundation of any AR-15 build. It is the part that houses the trigger, magazine release, bolt catch, and other internal components. By purchasing an 80% lower receiver, you are essentially buying a firearm without the serialized number, which allows you to customize and modify it to your heart’s content.
Tools and Materials Needed
Before you begin, gather the necessary tools and materials. You will need a high-quality milling machine, a solid vise, a set of end mills, a caliper, a scribe, a drill press, a drill bit, a file, and some cutting oil. It’s also essential to have a good understanding of the dimensions and tolerances required for the 80 lower receiver.
Step-by-Step Guide to Milling an 80 Lower Receiver
1.
Secure the Receiver in the Vise
Place the 80 lower receiver in the vise, ensuring that it is properly aligned and securely fastened. The receiver should be held in place with a soft-jawed vise to prevent damage to the receiver.
2.
Set Up the Milling Machine
Adjust the milling machine to the desired height and ensure that the end mill is properly aligned with the receiver. The end mill should be set to the correct depth to achieve the desired tolerances.
3.
Milling the Mag Well
Begin by milling the mag well to the correct dimensions. Use the caliper to measure the receiver and make sure the mag well is the appropriate width and depth. Once the mag well is milled, inspect it with the caliper to ensure it meets the required tolerances.
4.
Milling the Ejector Window
Next, mill the ejector window to the correct dimensions. This involves creating a slot in the receiver that allows the extractor to engage with the cartridge cases. Be sure to follow the manufacturer’s specifications for the ejector window dimensions.
5.
Milling the Firing Pin Hole
Use a drill press to create the firing pin hole in the receiver. The hole should be drilled to the correct depth and diameter, as specified by the manufacturer. After drilling, use a file to smooth out any sharp edges.
6.
Final Inspection and Cleaning
Once all the necessary milling is complete, inspect the receiver for any burrs, sharp edges, or machining errors. Use a file or sandpaper to smooth out any imperfections. Clean the receiver thoroughly to remove any cutting oil or debris.
Conclusion
Milling an 80 lower receiver is a rewarding and satisfying process that allows you to build a custom firearm to your specifications. By following this comprehensive guide, you can ensure a successful build and a safe, reliable firearm. Always prioritize safety and consult the manufacturer’s specifications throughout the process to achieve the best results.
