I was cleaning my rifle last night when I discovered that the rear action screw was loose, this is the action screw that is at the rear of the trigger guard. I attempted to tighten it up with an allen wrench only to find that it will not tighten down. I removed the screw to see if there was any thread damage or anything I was missing to find that it is not the same type of screw as the other two action screws, it is very similar to a wood screw, the other two action screws are similar to a bolt. I also discovered that the rear action screw threads straight into the plastic of the stock and is apparently stripped. I am rather new to all of this and need your expert advice, what can be done about this?

Thanks In Advance