I did my own test using a freezer and and oven. I found that the Extreme powders were no more stable than any other powder. In fact, in the 7mm wby I was using, RL 25 was more stable than Retumbo or H 1000. The Vihtvuori powders are supposed to be very stable and they were more stable in my test than the Extreme powders. I am not saying my testing was perfect but it was convincing enough to me that I am going to use the most accurate powder for the given rifle rather than bending over backwards to make the extreme powders work. For my 7wby it was RL 25.
