Your scope is junk. The fact that your shooting smaller groups but exactly 9 inches to the left or right seems to be the giveaway. Only way to figure it for sure is to hit the range again but till you get a new scope I would sight in at the lowest power and leave it there. Alot of older variable scopes had this problem where they didn't hit the same point of impact at different magnifications which is why older shooters were always so fond of fixed power scopes where such problems didn't crop up. A new quality scope or leaving it at a single power should eliminate this problem. Most major scope manufacturers eventually solved this problem which is why the bottom dropped out of the fixed power scope market. Alot of newer scopes still have the same problem but it is so small that no one recognizes it except target shooters which is why fixed power scopes still are a significant force in the target shooting market. IMHO. Hope it helps.