Here is the method I have used for 30 plus years !! All New scopes mounted & bore sighted If a gun shop & always insist they put a dab of Loctite on screws !! then take several boxes of ammo , various brands . Set up a target at 25 yards .. shoot .. rest 2 to 3 minutes .. shoot again .. & repeat once more { 3 shot groups } adjust scope accordingly . Once your shooting almost the same hole at 25 yards move to 100 & shoot several 3 shot groups with the various ammos note each group . DO NOT adjust scope once you have decided which ammo is giving you the best grouping move target to 200 yards .. Shoot 3 shot groups & adjust scope to tighten up groupings !! Also doesn't hurt to shoot some of the other brands at the 200 yards . Once you have your grouping down as tight as it will go Hopefully its at or under 1" at 200 yards move out to 300 400 or longer & shoot it will Amaze you how much of a spread that 1" group at 200 will increase at 400 yards !!