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From my prior post you see it's easy to find the BC that gives you the right drop at one other range. The magic of Dr. Oehler's software is that you can use drop at a third range to test that BC or discover other factors like small changes in MV that give a match.
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Thanks for the credit, but the "sliders" and easy solution were entirely the invention Richard Larson who has labored on "Ballistic Explorer" for many decades.

Ken O

As it was explained to me many years ago, "I feel sorry for those who believe that ballistics is an exact science. They just don't understand the problems."