Well, there are lots of factors to consider, like which ammo you'll use for one. That can make a big difference. Assuming you use some of the higher velocity stuff, I would sight it in dead on at 50 yds., then check it at 25 and 75. My guess is you won't need to change your aiming point at 25, but you may need to hold over a bit at 75. Then again, that's a long shot at a squirrel.