I agree with DrewBone. A few inches at 30 yards would be fine but 25" low is excessive. My guess is either something was loose or I have seen drastic shifts in POI like that with threads that are not concentric to the bore.
If the "can" shoots fine on other platforms, both a pistol and a rifle , then it is obviously not the can. That leaves the rifle in question and first thing i would look at is the "threads"? Are they straight, concentric etc?