Temperature will affect your range marking accuracy in many cases. The higher the mag, the more difference you will see (unless you won the scope lottery). Under 20x you typically won't see much of a shift. Ranging between 45 and 55 yards sucks on a lower powered scope anyway.
This is why you see guys that use 40-80x scopes for FT with a temperature gauge on the scope. They sometimes have different markings for different temperature ranges. Whereas people that shoot hunter class with a 16x max scope zoom don't typically worry about the temperature shift.
My Falcon T50 doesn't seem to shift much, but I can't recall the last time I had it out in less than 60 degree weather.
If you have a high mag scope, maybe an experiment to try would be to mark the scope at full mag and also mark it at 25x. Then check the two setting at different temperatures. It won't range find as well at 25x, but if the temperature shift doesn't affect it as much at 25x it could be a good back up plan. If the 25x markings are not as affected by temp, you could range a target at 40 yards at 25x, then zoom to the max and see if the max mark at 40 yards is correct. That might be useful on days that start out cold but warm up quickly. I may be talking out of my butt here, but it's Sunday afternoon and I have nothing better to do.
