Not very scientific, but I will say that if you lose your footing, and somersault and then tumble about 80 or 90 feet down a steep, rocky slope ( losing your rifle off of your shoulder on the first or second bounce), your rifle will definitely need to be sighted in again. It may also need some cosmetic attention, especially if it happened to land muzzle first on at least one bounce, and the scope will likely need to go back to the manufacturer for service.
