SaskBushMan
Me, myself, and I would go ahead and site it in at 25 yards to hit somewhere about and 1" high on the bull. Then shoot a group and see what type of group you get... then start increasing your powder shooting groups (normally 3 shot groups)... as you increase you powder charge the pattern should start climbing the target. When you get to the power level you want or like - site it in 2" high @50 - thenmove out - thisreally should put you really close @ 100 yards
Here is a ballistic chart for a moderate load on a
250 grain bullet that will give some idea about what it is doing... The 250 SW has a higher BC than the XTP so this info is not in stone.
Good luck - remember this is just me & there is more than one way to skin a cat...
mike