I have been wanting to buy a 20 ga 870 for my 10 year old for a little while now.  I have a burris speed bead scope to put on it and I have a Remington super full in the gun cabinet.  I know it would need to be drilled and tapped to mount the scope.  I also want to mount an adjustable stock on it so that I could also comfortably use it if I wanted to.  Lately I have been thinking I should also consider a Mossberg, or a Charles Daly as well.  I would still like the ability to put an adjustable (knox type) stock on it.  I know the mossbergs come already drilled and tapped so that would not be a concern.  Is there an adjustable stock set made for a 20 ga Mossberg?  Pattern wise, I really liked the patterns I got from a friend's 870 with the super full, can I expect good patterns from the Mossberg or Charles Daly and any of the cheaper chokes or will I need to buy a pure gold or sumtoy to get good patterns.  I have federal HW #7, hevi-13 #7 and hevi-13 #6 in the cabinet to shoot out of whatever gun I decide to go with.  I would really like to get it all set up for him for his birthday in mid March so I am starting to run out of time to make a decision.  Any help would be greatly appreciated.  Thanks.