How To Assemble AR15 Lower

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  • Post category:AR15
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This is a how to assemble AR15 lower guide from start to finish. Before starting, you may need these tools to help you successfully put together everything.

  • Roll pin punch
  • Small mallet hammer
  • Receiver vice block
  • Adjustable torque wrench
  • Staking pin (Optional)
  • Allen and hex screw driver
cmc lower parts kit with trigger

Step 1. Install Receiver Pins

  • Place the lower receiver in a receiver vice block to secure it.
  • Drive the receiver pins through the lower receiver using a roll pin punch and a small mallet hammer.

Step 2. Install Magazine Release Button

  • Locate the magazine release button and spring.
  • Assemble the magazine release button and spring in the lower receiver
  • Ensure that the magazine release button operates smoothly.

Step 3. Install Trigger Guard

  • Place the trigger guard into the lower receiver.
  • Secure it using the roll pin punch and small mallet hammer.

Step 4. Install Trigger Group

  • Place the trigger group into the lower receiver.
  • Tighten the trigger group using an adjustable torque wrench.
  • The challenging part is the hold the spring tension while trying to align the holes. A complete drop in trigger is the easiest to install.

Step 5. Install Fire Selector & Detent

  • Place the fire selector and detent into the lower receiver.
  • Secure it using the roll pin punch and small mallet hammer

Step 6. Install Pistol Grip

  • Screw the pistol grip into the lower receiver.
  • Tighten it using an Allen or hex screwdriver.

Step 7. Install Bolt Catch

  • Assemble the bolt catch and spring into the lower receiver.
  • Secure it using the roll pin punch and small mallet hammer.

Step 8. Install Buffer Tube 

  • Place the buffer tube into the lower receiver.
  • Secure it using the castle nut and end plate.
  • Stake the castle nut in place using a staking pin (Optional).

Step 9. Install Stock and Recoil Spring

  • Place the buttstock and recoil spring into the buffer tube.
  • Secure it by screwing the stock onto the buffer tube.

Be sure to know the difference between mil-spec and commercial buffer tubes

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