Mule Deer:
Wow, I have the same observations about IMR powders. I used to love IMR 4831, but I gave up on it. I used to have a house in MN and shot all year round, and you could definitely see the affect. It is hard enough a very long ranges to deal with the change in air density...trying to compensate for MV is just too much.
The worst powder I have ever seen is H335, but it shoots well in .223s, and I don't plan to use them in frigid temps.
Have you ever noticed the super slow powders in big cases (e.g., .300 RUM) produce high MV standard deviations?
