Re: 300 WM powder choice
I love IMR4831. It is my favorite powder in 243Win, 6mmRem, .25-06, and 7mm RM. In my guns, at least, it provides the best velocity/accuracy of any powders I've tried, including H1000 and the ReLoader series.
In my 3 .300 winnys, it seems to work best with the 150 and 165 gr bullets. R-22 edges it out in velocity when you move up to 180 and 200 gr. Accuracy in my guns at least, is on par with R-22 across the board.