Re: 257 Weatherby Mag
I have the same rifle set in a bc medalist stock. Mine had a definite preference for the 115 gr class of bullets.
I have never fired a factory round thru it but I settled on shooting a 115 bt with norma brass, fed 215, and retumbo at 3400. Oal is 3.34. If you want to try that load start about 71.5 gr and work your way up. I settled at 73 gr. Mine still copperfouls some so I clean about every 25 rounds. Accuracy has been 1/2 moa or better to 500 yds so far. 200 yd groups have been 1/2-1" consistantly.
I tried imr 7828, hybrid 100v, imr 4350 and h1000. Hybrid100 was best with the 100 gr bullets with velocity about 3550. If you want to shoot the 110's I would try h-1000 first. If you want any of the numbers let me know. I chronoed everything and found max loads in all of them for my rifle.