I have personally witnessed a factory rifle change the point of inpact by 6" at 100 yards due to the wooden stock shifting.The rifle was a 25-06 rem 700bdl that is owned by a former hunting partner of mine.The two of us checked our rifles one day prior to leaving on our annual deer hunting trip and his rifle was 3" high at 100 yards.We then drove to the hunting area the next day and scouted for a day before the season opened.On the second day my partner missed an easy 200 yard shot on a whitetail buck.Thinking that he just messed up we continued hunting.On the last day my partner missed another buck at between 250yards and 300 yards which should have been a relativley easy shot for him.Being suspicious,we set up a target and were amazed to discover that the rifle was now 9" high at 100 yards.Instead of bothering to rezero the rifle he decided to use his back up gun as he didn't really trust the 25-06 any more.After returning home the gun went into the gunsafe and remained there for a week until we could get to the range.To our amazement the poi had returned to 3" high at 100 yards after sitting in a warm dry house for a week.