Building your own AR-15 can be a rewarding experience, offering a deep understanding of your firearm and allowing for significant customization. This guide focuses specifically on assembling the lower receiver, the serialized and regulated part of the rifle. Remember: Always follow all applicable federal, state, and local laws and regulations regarding firearm ownership and assembly. This guide is for informational purposes only and should not be considered legal advice. Improper assembly can lead to malfunction and potential injury.
Tools and Parts You'll Need
Before you begin, gather all the necessary tools and parts. You'll need:
- AR-15 Lower Receiver: This is the foundation of your build. Ensure it's a stripped lower receiver, meaning it doesn't have any parts installed.
- Lower Parts Kit (LPK): This kit typically includes the trigger, hammer, disconnector, safety selector, bolt catch, magazine catch, and their associated springs and pins.
- Buffer Tube: This houses the buffer spring and buffer.
- Buffer Spring: This spring propels the bolt carrier group rearward.
- Buffer: This absorbs the recoil energy.
- Castle Nut: This secures the buffer tube to the lower receiver.
- End Plate: This covers the end of the buffer tube.
- Appropriate Punches and Tools: You'll need punches (roll pins are best) for installing the pins, and possibly a receiver block for easier assembly. A torque wrench for the castle nut is also highly recommended.
Step-by-Step Assembly Instructions
This process is best understood with visual aids. Consider referencing videos and diagrams alongside this guide.
1. Installing the Hammer and Trigger Pins:
- Lay the lower receiver flat.
- Insert the hammer pin from the right side, ensuring it passes completely through.
- Insert the trigger pin from the left side, ensuring it also passes through completely.
- Note: Some LPKs may have the hammer and trigger pre-assembled; if so, this step is simplified to installing the single trigger/hammer pin.
2. Installing the Safety Selector:
- Insert the safety selector lever into its corresponding slots on the receiver.
- Ensure it moves freely between the "safe" and "fire" positions.
3. Installing the Bolt Catch and Release:
- Install the bolt catch pin from the right side.
- Install the magazine catch, ensuring it's seated correctly.
4. Installing the Grip:
- Align the grip with the lower receiver.
- Secure the grip using the grip screw.
5. Installing the Buffer Tube:
- Carefully insert the buffer tube into the receiver extension.
- Secure the buffer tube with the castle nut using a torque wrench (recommended torque specifications will vary by manufacturer). Over-tightening can damage the receiver.
6. Installing the Buffer Spring and Buffer:
- Insert the buffer spring into the buffer tube, followed by the buffer.
- Ensure the spring is properly seated.
7. Final Checks:
- Before proceeding, perform a thorough inspection of your work. Check that all pins are securely seated and that all components function smoothly.
- Check the trigger pull for proper function and smoothness.
Important Considerations
- Lower Receiver Serial Number: Understand the legal implications of owning and assembling a firearm. The lower receiver is the regulated component.
- Torque Specifications: Always consult the manufacturer's instructions for torque specifications. Over-tightening can lead to damage.
- Safety First: Handle firearms safely and responsibly. Always treat every firearm as if it were loaded.
This comprehensive guide provides a solid foundation for assembling your AR-15 lower receiver. Remember to consult additional resources, especially video tutorials, for a more visual and thorough understanding. Always prioritize safety and adherence to all applicable laws and regulations.
