In the article (and book chapter) I suggest sighting-in an inch low at 25 yards works far better as an initial zero--which usually results in about a 35-yard zero.
Another thing I mention is that a 25-METER sight-in is taught in at least one of the South African professional hunter schools. I found this out on a 2003 safari, when the assistant PH was a recent graduate of the school. He took our group to the ranch range, where he had a target set up at 25 meters (a little over 27 yards), and insisted it would work fine. I tried (mildly) to correct him, but that obviously wasn't happening. So I deliberately held an inch over the bullseye--but just about everybody else's rifle shot too high in the field, and had to be corrected. Four years later I hunted with the same young PH on another ranch, who by that time was out on his own. He took our group to the range he'd set up--which turned out to be 100 meters, not 25. I didn't say anything, but he looked at me and grinned.
Another problem with the 25-yard sight-in (or any trajectory calculation involving the height of the scope) is that even many hunters who measure scope-height do it wrong. The usual mistake is measuring to the bottom of the scope, not the centerline. In fact a lot of people somehow can't figure out how to measure height to the centerline even when that's what they're trying for. Don't know what's so complex about it, but have seen that a number of times.
