I helped a guy I know sight in a 300 Weatherby,He wanted to get to 800 yards but his scope,a Conquest 6.5-20x50mm,was mounted on a zero base.We ran out of up at 650 yards.We did 50 yard increments from 200 yards on out so he could get his drops just right.When we got done at 650 I carried the target board back to 100,our starting point,and made him shoot his last group of the day.Zero was still zero.Just like it should be.
Hes been runing that same load and set up now for the past 5 years.Its worked out very well for him.
dave

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Only accurate rifles are interesting.