I'd pick a grain size you intend to use with the 270win. Start at 25 yards, adjust so you acheive a grouping approx -1"(below) the bull and then move to 100 yards for fine tuning/adjustments for zero. Most of my rifles sit at +2" at 100, that allows me to have a MPB of 300 yards (without hold over). Though it dependsentirely on your situation,say a 200 yard shot is the max that you'd see no real need to site in for further ranges.
I assumed that your scope was boresighted when mounted but an easy test is to place an orange dot on your target at 25 yards, then remove your bolt and place it in a solid rest position. By looking through your bore line up the centre of the bore with the dot and without moving the rifle raise your head to see if the crosshairs are approx. in the same position. If not you can adjust them to match what you see through the bore to acheive bore sighting. Then fire groups/fine tune as per normal. (a second pair of hands is helpful for this procedure if you don't have a gun vise or rest that helps stabilize the rifle easily).
Good Luck and enjoy
tips 4 sighting in a new rifle?
