H-4350, for all those bullet weights.
IMR4350 will work just as well, and may even shoot a little more accurately with some bullets, but H4350 works through a powder measure quite well and is less temperature-sensitive.
Other powders work very well in the .257, especially Ramshot Big Game and Hunter (and even Magnum, with 115-120 grain bullets). But H4350 is always the first one on the list.
