What I am wondering is what powders work best and what bullets?
Been reloading the .300 Win Mag since 1965: Did extensive load workup back then. i use IMR 4831 almost exclusively for reloading 150 grain, 165 grain and 180 grain bullets. For infrequent use with heavier bullets i use IMR 7828.
Saskhunter is right about .300 Win Mag case life.