If you are going to shoot at 100 yards, sight it in at 100 yards. A 25 yard sight-in isn't always going to be indicative of what group you'll get at 100. I've seen that too many times with rifles. It ought to print well at 100, but it doesn't. Why? Well I guess we can discuss it forever, but back to the point that matters. Sight it in for a 100 if you are going to shoot at 100.
Of course, you don't have to listen to me (and some of the others), but remember this when the big buck runs off. We told ya....