Hi Ed---I had a similar problem with a cheap/rough Bsa cadet. It would seem to group in two places, then you would get a really wild flier. I tried to tap down the dovetails (and yes even popped them) but the bugger was still the same. I even put a drill down the end of the barrel about 1/2 inch as it was pitted. I soldered the foresight in place but it came loose. I then got a new foresight and it cured the gun------Even my barrel drilling had not seemed to have made the gun worse. I think that both the sights were a poor fit at first and then just the foresight and it was ok for a shot or two and would move. Maybe just check the sights are tight before looking for anything else?