I've been reloading .270 for years now. Although it's almost a cliche at this point, H4831(SC) really is a fantastic powder for this cartridge. I've tried two or three other powders, with decent-to-good results, but always went back to H4831.
For a while, I attempted to shoot Very Long Distances with the .270, using Sierra's 135 grain MatchKings. I ultimately acheived really outstanding accuracy out to about 600 yards, sometimes 700, but no farther. At 1000 it was a real crapshoot, and was highly inconsistant, due partly to insufficient bullet weight. I wish someone would design a high-BC match bullet that was up above 150 or, ideally, 160 grains...