Reloder 22 is a great powder in the 7mm RM for the temperatures you hunt in. If it's working for your rifle, I wouldn't change it.
Temp-resistant powders are really only useful when temperatures range 100 degrees or more, and even then may only make a difference at ranges beyond 300 yards, which is as far as most hunters tend to shoot.
If you want some recommendations for other powders I can provide 'em, but it's hard to beat RL-22 for your purposes.
