TheArmedScotsman TheArmedScotsman

Step by Step AR15 Lower Receiver Build Guide

The “tool” is called a clevis pin 1/4″ x 2″
Buy the M4E1 lower here: https://bit.ly/3cZWMqw
M4E1 MOE Lower Parts Kit: https://bit.ly/3mEQNfZ

 

This is a simple guide. Please make sure you follow all safety procedures.

AR-15 Lower Receiver Build Guide: Step by Step

Tools and Materials Needed:

  1. Tools:
    • AR-15 Lower Receiver Vise Block
    • Small Hammer
    • Roll Pin Punch Set
    • Armorer’s Wrench
    • Allen Wrenches
    • Takedown Pin Tool (optional but helpful)
    • Small Flathead Screwdriver
  2. Parts:
    • Stripped Lower Receiver
    • Lower Parts Kit (LPK) which includes:
      • Trigger Group
      • Bolt Catch Assembly
      • Safety Selector
      • Magazine Catch Assembly
      • Pivot Pin
      • Takedown Pin
      • Buffer Retainer and Spring
      • Trigger Guard
      • Pistol Grip and Screw
      • Buffer Tube Assembly (includes buffer, buffer spring, end plate, and castle nut)
      • Stock (if not using a pistol configuration)

Step 1: Install the Magazine Catch

  1. Insert the Magazine Catch Button and Spring:
    • Place the magazine catch into the slot on the left side of the lower receiver.
    • On the right side, place the magazine catch spring over the threaded end of the catch.
    • Screw the magazine catch button onto the threaded end of the catch, compressing the spring slightly.
  2. Tighten the Magazine Catch:
    • Press the magazine catch button in and rotate the magazine catch on the left side clockwise until it is flush with the receiver.

Step 2: Install the Bolt Catch

  1. Install the Bolt Catch Spring and Plunger:
    • Insert the bolt catch spring into the recess on the lower receiver.
    • Place the bolt catch plunger on top of the spring.
  2. Install the Bolt Catch:
    • Align the bolt catch with its hole, and carefully start the bolt catch roll pin using a roll pin punch.
    • Ensure the pin is flush with the receiver, being cautious not to scratch the lower.

Step 3: Install the Trigger Guard

  1. Insert the Trigger Guard:
    • Place the trigger guard into the lower receiver, aligning it with the holes.
  2. Install the Trigger Guard Roll Pin:
    • Carefully tap the roll pin into the hole using a roll pin punch, securing the trigger guard to the lower receiver.

Step 4: Install the Front Pivot Pin

  1. Prepare the Detent and Spring:
    • Insert the pivot pin detent spring into the small hole on the front of the receiver.
    • Insert the detent on top of the spring.
  2. Install the Pivot Pin:
    • Use the pivot pin tool or a pair of needle-nose pliers to depress the detent, and slide the pivot pin into place, capturing the detent.

Step 5: Install the Trigger Group

  1. Install the Trigger and Disconnector:
    • Insert the trigger into the receiver with the disconnector on top. Align the holes and insert the trigger pin.
  2. Install the Hammer:
    • Place the hammer into the receiver and align the holes. Insert the hammer pin to secure it. Ensure the hammer spring is correctly oriented, with the legs resting on the trigger pin.

Step 6: Install the Selector and Pistol Grip

  1. Install the Safety Selector:
    • Insert the safety selector into the hole in the lower receiver.
  2. Install the Detent and Spring:
    • Drop the safety selector detent into its hole.
    • Place the safety selector spring into the hole in the pistol grip.
  3. Attach the Pistol Grip:
    • Align the pistol grip with the lower receiver and secure it using the grip screw. Ensure the safety selector functions properly.

Step 7: Install the Rear Takedown Pin

  1. Prepare the Detent and Spring:
    • Insert the detent spring into the hole at the rear of the receiver.
    • Insert the detent on top of the spring.
  2. Install the Takedown Pin:
    • Slide the takedown pin into place, capturing the detent and spring.

Step 8: Install the Buffer Tube Assembly

  1. Install the Buffer Retainer and Spring:
    • Drop the buffer retainer spring into its hole at the rear of the lower receiver.
    • Place the buffer retainer on top of the spring.
  2. Thread the Buffer Tube:
    • Begin threading the buffer tube into the receiver until it holds the buffer retainer in place.
    • Align the end plate and thread the castle nut onto the buffer tube.
  3. Secure the Assembly:
    • Tighten the castle nut with the armorer’s wrench.
    • Insert the buffer spring and buffer into the buffer tube.

Step 9: Attach the Stock

  1. Install the Stock:
    • Slide the stock onto the buffer tube.
    • Secure it using the stock’s adjustment mechanism or a provided screw.

Step 10: Final Checks

  1. Function Test:
    • Ensure all parts are installed correctly by performing a function check. Test the trigger, safety selector, magazine catch, and bolt catch.
  2. Check for Proper Assembly:
    • Visually inspect the lower receiver to ensure all pins are flush and all components are securely installed.

Conclusion

Congratulations! You’ve successfully assembled an AR-15 lower receiver. Ensure everything functions properly and double-check all screws and pins are secure. Your lower receiver is now ready to be attached to an upper receiver for a complete rifle.