.243 Brno sighted in, used for years never sighted in again. .308 Heym- Ruger used for 35 years only checked and resighted if there was a change in my reloading and that was rarely. Mauser M03 .308, 3 scopes on their own mounts, change scope shoot the chosen ammo for scope always shoots to point of aim. Merkel double rifle, sighted in, I have 3 different load for it that all shoot to the same point of aim. The amount of times that I've seen people chasing bullets round a target twiddling knobs then leaving at the end of a shooting session then doing the same the next time with not a clue. One bullet weight for all shooting occasions set up the rifle then leave well alone.