Not to product plug, but vortex now makes a rangefinder that does the same thing as the sig. Also has a mapping feature with thier app that will drop a pin at you target to help you get to the right spot. But the big deal is it runs in the $700-$800 range. Might be easier on your customers.
What I do is for every 100 yards say 300 yards, allow for 2 inch drift, for 800 yards allow for 7 inch drift and so on. So basically subtract one inch for the first number in your distance. Not just the wind it is a correlation of wind and barrel twist. Imagine how a pitcher throws a curve ball. He puts a spin on the ball much like the barrel twist does to the bullet. Given different projectiles have different affect. Just learn the bullet.
Generally speaking, lets say for a moment you have NO wind at the moment you shoot at a target that is 800 yards out, what do you hold for spin drift alone? Take a 7PRC, 175 ELDX at 2925 fps and for whatever reason there's not even so much as a cross - breeze from your muzzle to the target, at what distance do we need to take spin drift into account? I think I was told 600 yards at 500-1000 feet elevation, and to hold about a half minute at 800 solely for spin drift.
If you zero at 200 the average spin drift at 800 would be around 2-3 inches . I try and zero the rifle at 600 so I shoot a bit left at say 300 and a bit right at 800. By a bit I’d say 1.5 inches . So hardly enough to have to worry about in hunting situations it till close to a 1000.
