An item I would offer for consideration is the actual rangefinder one is using. I'm not talking about Sig vs Leica, I'm talking about the exact unit in your hands.... For example if I range and true my ballistics with my Sig rangefinder, I would never trust my buddies rangefinder even if it were the exact same model. Once I've trued my hardware system, any change in that system is another variable that has to be verified.
Very true. I have a Terrapin-X, and a buddy got an Sig Kilo 10K. We were ranging the same targets one day with them. At distances around 1000 yds, he was getting consistently about 4-5 yds more than me. At around a mile to 2000 yds it was 9-10 yds more than mine (that's enough to put you way off on your solution).
So, back at my own range with multiple targets out to 1626 yds, we had them professionally surveyed with modern surveying equipment that is accurate to about 0.5 inches. So now we have KNOWN distances that we can use to test range finders. It turned out that my farthest target (1626.27 yds in the survey), ranged consistently (and still does) at 1625 with the Terrapin-X, and 1635 with the Sig 10K. He sent the 10K back to Sig, they sent him a new one. It was better, but still off by 5 yds.
The Terrapin-X error shrinks to less than a yard at distances around 1200 or less. I assume that error grows to probably around -2 yards by the time you're out to 2100-ish, but can't confirm because we don't have anything surveyed that far. I'm just extrapolating the error at shorter distances to arrive at that figure - 0.5 yds short at 1219, 1 yard short at 1626, so presumably 2 yards short at 2100.
Here's the FUNNY part. He bought the 10K because he had a Sig Kilo 2400 that wouldn't range small targets much past 1000. Once we got the survey done, he tested it and accidentally found out that if he aimed the reticle a certain distance to the left (I think it was left), all of a sudden it started picking up all those targets he couldn't range before, AND, it was the most accurate of ALL the ones we tested - dead on (to the nearest whole-yard) with the surveyed distances at 740.xx, 1147.xx, 1219.xx and 1626.xx yards. He sold the 10K and knows how much "windage" to hold on the Kilo 2400 to account for the beam/reticle misalignment and get accurate returns from the target.
