Everyone usually mentions IMR4831 or IMR4350 right away. I prefer an old favorite: Winchester 760. I love the way Winchester's ball powders meter. Under some Sierra 140gr. Game King bullets, the 760 load produced 100-yard four-shot groups of .79 and .88 inches today. And these groups were out of a semi-automatic; a Belgian/Portuguese Browning BAR. My stash of 760 is old enough that it's packaged in metal cans. The Sierra Game Kings are not "premium" bullets but they have never failed me as far as accuracy and performance on game are concerned. I've killed a bunch of whitetails with them. If you're having trouble working up a good .270 load, you might want to give 760 a try.