Re: Most temp stable powders for 06 and Mag size cases
H380 is very temp sensitive in my experience as well. But I think all powders, extreme or not, are temp sensitive to some degree. Ambient air temp will change the burning rate of powder regardless of what coatings are used. I use Hodgdon's extreme line H4831sc in my wildcat .22 all year long, and it has to be loaded close to max to attain any accuracy. I have to "chase" that certain pressure from 90 degrees to 35 degrees, and I usually have to load up about 2 grains for this time of year (winter)! That might be less of a change than if I use RL19, but it still changes.
If it's not far, it's boring.