I need to carefully read what you posted. lol I was talking about the small socket screw that would be hidden if the stock is not removed.
You can just pull down the lever until it clears the groove that it sits in. Extend the stock in the fully extended position and pull down hard on the lever till the stock slides itself off from the pipe.
Here's a link to the M4 manual and exploded view of the parts:
http://www.airsoftplayers.com/m4/m4_1.jpg