I've been using free Pointblank software for a number of years now. One of the things I use it for is just this sort of thing. I sight in at 25 yards. However, before I do, I crank the load through Pointblank and figure out how low to the bull I should be shooting at 25 to be an inch or two high at 100 so that I'm close to dead on at 200.
One or two shots at 25 yards confirms that I'm at least going to be close at 100 yards.
