Two things I can think of are, one, how tight is the middle action screw ? It should be only snug, not any tighter than that. Do the front action screw, then the rear and check the middle one.
Second, if you are sure the scopes are good, then I'd look at first the barrel crown, and then the rifle's chamber.
Just for the record, I've hunted throphy deer with ammo that wouldn't shoot better than 2.5 inches with my M70 Fwt., .308. That's because of the bullet I insisted on using. However, it will shoot from .5-.8 for three at 100 yds. with ammo it likes. As rule, an inch or so for three should be quite possible. E
