Finally got to the rifle range to test my .257 Wby Mag loads. I was shooting 80 grain Barnes TTSX bullets over the following charges (use at your own risk), and I'm getting 1 MOA and under so far. Looks like this rifle really likes H1000 (.5 MOA group) but IMR 7828 is the velocity champ!

80g TTSX 80g H1000
3889 3831 3805 3805

80g TTSX 68 H414
3736 3775 3814 3813

80g TTSX 76g 7828
3983 3946 3963

Also shot my .458 Lott with the bulk Remington 405 grain SP over 22 grains of Trailboss for 1,100 FPS. What a riot! Like throwing pumpkins! Just to see if it could be done, I also shot this rifle off the bench with the same bullet loaded over 77 grains of XBR. It literally knocked the spit out of my mouth! Standing-only proposition in the future with any load above 2,200 FPS!