Keith,
Joel doesn't use different forearm positions to tune differentially for different distances. He just looks for the place that gives the least vertical at any distance. ARs like to be supported very close to the mag well. So does the Swede 96 that I shot with success in factory class at Hawks Ridge a few years ago. Most factory guns like up close. That is lot different than most bench type rifles. You can also get rid of vertical by making sure your front bag doesn't get packed too hard.
The point I'm trying to make is that differential tuning for different yardages lovely theory but practical nonsense. The tune of a bench rifle will change with wear faster than you can generate statistically significant differential distance tune data that isn't corrupted with noise from conditions that are always present at 600 or 1K yd (John Lewis' 600 yd. record group excepted).
The old legend of two piece stock hinge in the middle Enfield rifles shooting crap ammo better than the normally more accurate Springfield rifles at 1200 yd. may be true but it doesn't apply here or anywhere else you or I are likely to shoot.
A shooter looking for advice on this board would be misled to believe he should tune only at the distance he intends to compete at. A good 200 or 300 yd. vertical tune in a predominantly crosswind condition (so he can believe what he is seeing at that distance) will equip him to learn from the shots that don't go where he meant them to. Once he can believe what the rifle is telling him he can reduce his mistakes behind the gun and advance his craft.
Your very complicated approach for differential distance tune is merely a barrier to entry to someone that would be unfortunate to believe it, and why I asked if you used it yourself.
Greg
