ORIGINAL: Briman
I like to sight in for windage at 50 yards, then check it and touch it up at 100 yards if it is a calm day.
From my experience, being on at 25 yards will put you very close at 100, being on at 50 will put you about 5-6minutes high at 100.
I was talking windage (left to right) not elevation. I like to use 50 yards to start with for windage because wind doesn't effect it that close, especially with slug guns and ML's. And windage really shouldn't change much as distance increases as long as it's calm out. It may need touched up a bit though. Elevation is what changes as distance changes and needs to be varified at the distances you actually intend to shoot at.
That has always been my theory anway.
Paul