The action spring in an AR-15 semi-automatic rifle helps reduce recoil when the weapon is fired, then supplies the force that drives the bolt carrier and bolt back into battery to chamber a new round of ammunition. The action spring operates inside of the rifle's buffer tube, a thin metallic cylinder secured inside the lower receiver extension that runs into the AR-15's butt stock. In order to give your AR-15 a detailed cleaning, you need to remove both the action spring and buffer tube from the rifle.
Items you will need
Gunsmith's drift pin
Step 1
Place the AR-15 in a vertical position, with the back of the butt stock resting on a stable work surface. Push down on the slip ring at the base of the handguards, then remove the handguards.
Step 2
Use a drift pin to press in the take-down pin as far as it will go. The take-down pin is located on the left rear of the receiver, just above the fire selector switch. Swing the back of the upper receiver away from the lower receiver.
Step 3
Push in the receiver pivot pin and slide it out from left to right. Separate the upper receiver assembly from the lower receiver. Set the upper receiver aside.
Step 4
Locate the buffer tube retaining pin at the back of the lower receiver. It's at the bottom of the receiver, in front of the opening to the AR-15 receiver extension (the metal tube that extends into the butt stock).
Step 5
Push back on the buffer tube with your finger, then depress the retaining pin with a drift pin. Slide the buffer tube and action spring out of the receiver extension.