Hi Jerry,
Very interesting!
I eventually came to a similar conclusion on a caribou hunt in Quebec in the early 1990s. It was an "affordable" almost-DIY hunt, common then in Quebec: You brought your own food, and hunted and packed out game on your own, but were provided wall tends with cots, a primitive kitchen, and a "camp manager" to fix stuff, provide a little hunting advice, and use a 2-way radio for emergencies.
We'd already seen from the air as the plane approached that the camp was surrounded by caribou, and when it pulled up to the shore the camp manager (a French-Canadian named, of course, Pierre) was very excited. "Get your rifles and go! These are the first caribou to appear in many days!"
So we did. The camp, however, did not have any sort of target set-up to check zero, so I grabbed emptied one of our grocery boxes, and used my note-pen to draw a small circle, setting the box down 50 of my paces away. (I limited it to 50 because the only flat ground was a narrow strip along the shore. Behind the camp a semi-mountain rose pretty steeply.)
I did some mental figuring. The rifle had been zeroed two inches high at 100 back in Montana, so should shoot slightly high at 50. It did, and worked fine in the field, shooting just about dead-on at 200-225.
Did some more experimenting after that, and discovered the 25-yard sight-in recommended by O'Connor (and many others) usually ended up with a 100-yard zero higher than three inches, often 4-5 inches, depending of course on the cartridge, and how high the scope was mounted over the bore. In general, short-range zeroing at 35 yards comes much closer to the present standard for big game rifles of two inches high at 100--which of course results in shots landed a little high at 50!
Hope you are doing well. I supposedly semi-retired this year, resigning from one of my magazine markets that required half my writing time, but only provided 1/4 of my income. But it still feels like I'm working way more than half-time!
