Here the Stock Retaining Ring is fully seated. I tap on the Stock Retaining Ring with a large flat punch and a small hammer to make sure it is seated fully.
12. Reassemble the weapon
Perform a function test of the weapon to ensure that it is functioning properly. Ensure that you properly lubricate the Receiver after degreasing the action. You'll notice a difference when you pull the bolt to the rear if you haven't re-lubricated the weapon. I would recommend testing the safety, trigger and disconnector.
That concludes the tutorial on how to disassemble and reassemble the Receiver Extension on the Benelli M4. Hopefully it was clear and will be of use to some users in the future. I will leave the photographs up as long as photobucket remains free.
The way the M4 was meant to be.