I agree with bandg about first making sure it isn't just the wind. It takes only a 3mph wind to push a pellet over 2 inches at 80 yards, and that's a breeze that is nearly imperceptible without the benefit of an instrument.
Otherwise the most common cause is cant error, be it scope cant or gun cant. Spin drift would not have nearly such a dramatic effect at 80 yards.
First, regarding scope cant...
Set your scope to its maximum magnification and its parallax to 10 yards. Step back half that distance, 5 yards, from a mirror and look through the scope to view your reflection in the mirror. Confirm that the vertical bar of the reticle perfectly bisects both the objective bell and the muzzle simultaneously. If it doesn't, you need to loosen the rings and rotate the scope until it does (note: center the windage turret before you do). Use a rest so your reflection is nice and stable.
Then for gun cant...
Install and use a level. View a known good plumb line (e.g. hanging string) through the scope and orient the rifle so the reticle precisely aligns to it. Now secure your level so it shows level. From now on when you're shooting, hold the rifle so it shows level and you can be sure you've eliminated both potential sources of cant error.
By the way, don't buy a level that attaches to the scope rail. There is no guarantee it will show level. Instead, get one that attaches to the scope tube so you can rotate it and lock it down where it shows the proper level.
