RE: Sighting in a .243
Mainly personal preference. I set all my rifles dead on at 100 and then just hold over to compensate for distances beyond that.
My ballistics software says setting it 1.37" high at 100 yards will have it hitting dead on at 200. That's using Remington ammo loaded with 90 gr. Nosler ballistic tips. Most people I know try to set their rifles to hit dead on at 200.