Re: Temperature Sensitivity
A very reliable source has told me Ramshot Magnum is a very temp stable powder. Retumbo is also a great choice in the 300 as is 7828SC.
I personally have yet to find a reason not to use IMR powders based on temp stability. IMR, for the first 12 or so years of reloading was my first powder choice and I still keep a good 10 pounds of it on hand in 4350, 4831, and 4064.