When I had my coveted .270 decades ago, I asked Sierra Bullets' ballistic tech what powder he used to get best accuracy with that round testing all their .270 bullets. His answer was IMR4350 for 130 and heavier bullets, IMR4064 for anything lighter. He did say a bit higher muzzle velocity with 4831 was normal, but it never produced the accuracy the other two did; especially with the lighter bullets. He preferred 40% smaller test groups than 50 to 75 fps faster bullets. And that no ball powder was good for best accuracy.
US Navy Distinguished Marksman Badge 153
Former USA Palma Team Member
NRA High Power Long Range High Master
NRA Smallbore Prone Master