I have a Vortex Strikefire on my "15-22", fits just fine, the rail should work just as well with a different scope.
I don't think I could get it on my M&P22 though!
BTW, the A3 A4 upper is the one with the full length rail, instead of a carry-handle rear sight. I don't know if you can get the 15-22 with one of those, though. Could be wrong.