I have read a few posts on here mentioning that a scope must be shimmed to get enough adjustment for long range on some caliber/setups. I am shooting a 30-06 plain old stock rifle using a cheap 6-24x Tasco. I plan to move to a Nikon soon. My question is three fold. How do I know if a particular scope will need shimmed? Do they all need it for this caliber? The last question is about the alignment of the scope. If it is canted one way or the other, it would create horizontal movement when adjusted up or down. How can I tell if it was mounted correctly? The only real option I have is a larger gun store. They have on occasion bore sighted rifles that barely hit a 4'x4' target at 100yds, so I lack faith.