Nomercy is absolutely right. You cannot sight in at 25 yards, and then be able to say with any certainty whatsoever where it will be at 100. I have had rifles be pretty close at 100 after sighting in at 25, and then I have had them off the paper at 100. The only way to know for sure where it will be at 100 is to shoot it at 100. Shooting it at 50 will help somewhat, but really you need to shoot it at 100.

Vinny