mnimrod,
The problem with Reloder 22 (and other rather temperature-sensitive powders) isn't always just in longer-range shooting. Some rifles will change point of impact significantly even at 100 yards from 70 Fahrenheit to zero. I've seen three inches twice during my testing, and 1-2 inches isn't uncommon. Usually the rifles that do this are those that also change POI significantly with a change of a grain or two in the powder charge while working up loads.
This may not seem like much but the shift will be three times as much at 300 yards.
