I would want to do the test with tight chokes (if it is choke tubed) at fairly close range, maybe 20 yds. Do it at least ten times on the same piece of paper. It will actually cut a hole in the paper if you are consistent with your hold point. That will give you an accurate picture of what is going on. If one barrel is truly shooting to a different POI than the other, it would be expensive to change, as brother Harry suggests, and would involve stripping and relaying the ribs and releveling them but not refitting the ribs or the barrels. Then a clean up and reblack. If its a good gun and you like it, it might be worth it. It could be that both barrels shoot high and then you are getting into a stock fitting issue; that's not a big thing. It may just be a matter of bending the stock to fit you. Hope this helps.
