What powders do you find best for accuracy? ... likely will focus on 87-100 grainers.
After 40+ years of loading 'da Bob', if forced to pick just one powder for this range of bullet weights, it would have to be H4350, although I burned lots of IMR4350 before the H-version became available, and it worked very well.
However, especially for bullet weights <=100 grains, I've also used plenty of 4895 (H & IMR) and IMR4064 in this cartridge, and those powders have produced very good accuracy with velocities within 100 fps of that produced by the 4350s. Varget is another powder that I've used in similar cartridges, and I suspect it would produce excellent accuracy and acceptable velocities in the 257 Roberts.
