I have found that when I practice at my hunting camp I will have to adjust my windage every time. I will impact approx. 3" left at 40 yds. When I return home, I will be right by that amount and return the windage to the original setting. I hunt in the mountains and wnat to know if the thinner air at the higher altitude is the cilprit or am I just nuts! I shoot 4" right helical vanes.