I had the same problem with a pistol. (Shot to the left at ranges past where I sighted it in) I inspeted the barrel. The rifling on mine came out of the barrel on one side.
I took an old socket (7mm I think) that just fit inside the barrel. It was also flared out so the whole thing would not go inside. I put some oil on it and mounted it in a drill. I then set the drill to reverse,(To match the rifling twist) and slowly took off the edge. (Use for a 2-4 seconds then re-oil the socket) Now it shoots to point of aim.
I did this because I needed a new barrel, and had nothing to lose. If it worked GREAT if not I still had to replace the barrel.
Or you may want it checked by a gun smith??