I have been watching YouTube videos on long range shooting. Primarily Barbour Creek shooting school. They did an episode where they illustrated how much a 10-15 degree cant can affect impact at 1,000 yards. What I am wondering is how much will it affect 500 yards, 400 etc? Is this a linear thing where 500 would be off half as much as 1,000? Main reason for asking is if I do not shoot beyond 600 yards, is a scope level absolutely necessary?