Ballistics programs will ask for you to fill in the blanks on a number of variables to give you the information you need to be zeroed at 100 yards, but you need to know the muzzle velocity, bullet weight, bullet coefficient, and particularly the scope's height above bore.
More than likely at 50 yards you should be a little low with an average scope height of 1.5". If you're shooting off an AR-style platform with a higher scope height, say 2.6", you'll be considerably lower.
If you're going to be shooting at the longer ranges, I'd consider going to a 150 yard or 200 yard zero.
XD-40 service, XD-9sc, member GeorgiaCarry.Org, National Rifle Association, Gun Owners of America, North American Hunting Club, Rocky Mountain Elk Foundation
Last edited by treehugger49; 10-09-2012 at 01:40 PM.