Re: .264 win mag
Retumbo and 140 grain bullets has been among the top combinations in the .264WM until very recently. Other powders that give good results in the .264 are: H-1000, IMR 7828, and RL-25.
Keep your eye on RL-33. Its recent introduction may prove to be just the ticket for the .264WM. I haven't had the chance to work with it yet, but others are reporting excellent results.