absolute must. there is a big difference between 50 and 500 yrds. If you site it in at 100 you will not like what you see at 300. Will not be clear, kinda like mirage. It will take away from your ablility to score a deer also.
Also don't skimp on the rings and bases. Use steel rings and bases. Have a shop put them on to spec. Warne makes a good product and the price is right.