How to Replace the Forearm on an AR15

The AR15 civilian rifles derived from the military M16 feature a pair of polymer plastic forearm halves that shield the barrel, clamped together by tension from the delta ring. These guards protect the shooter from burns and provide a stable grip for holding the weapon while aiming. A frequent reason for replacement of stock AR15 forearms is to add aftermarket forearms with Picatinny rails for mounting a variety of tactical accessories like night vision equipment and sights.

Things You'll Need

  • Assistant
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Instructions

  1. Removal

    • 1

      Separate the upper receiver and barrel from the lower receiver. Wrap the upper receiver in a towel to make it easier to hold on to.

    • 2

      Stand the upper receiver in a vertical position, muzzle up.

    • 3

      Squeeze the delta ring at the base of the forearm between your thumb and index fingers. Pull the delta ring down, compressing the weld spring, until the ring clears the mounting tabs on the forearm.

    • 4

      Ask an assistant to pull the two halves of the forearm apart as you continue to hold the delta ring down.

    • 5

      Release the delta ring slowly to decompress the weld spring.

    • 6

      Pull the front ends of the forearm halves out of the end-cap and separate both halves from the receiver.

    Installation

    • 7

      Insert the ends of the new forearm halves into the end-cap, making sure the correct half of the forearm is on top of the barrel.

    • 8

      Stand the rifle vertically, muzzle up.

    • 9

      Squeeze the delta ring at the base of the forearm between your thumb and index fingers. Pull the delta ring down, compressing the weld spring.

    • 10

      Ask an assistant to push the two halves of the forearms together so they enclose the barrel, with the mounting tabs within the radius of the delta ring.

    • 11

      Gradually release the delta ring to lock the mounting tabs beneath it and decompress the weld spring. Pull forward on the delta ring slightly to make sure it is fully locked over the tabs.