Free: Contests & Raffles.
Using a 210 Berger @ 3100fps there is an 18" difference in point of impact at 1000yds going from 4000' ASL to 10,000' ASL. Going from 2000' ASL to 4000' ASL there is 10" difference in impact. Really, if you are going to enter all your conditions into a program to get a conversion factor, there isn't any reason to not just dial for your shot. Your basically doing the same thing.