I've tried mostly Berger bullets, 168 and 185 gr., and now find that since Weatherby's have such a large freebore, the Bergers may not be suited to the gun.
That certainly narrow the range of Berger Bullets. I think you might take advantage of that freebore by trying Berger's 230 grn bullets. They have two, the 230 Gr Hybird (BC G1 .743, G7 380) and the 230 Gr Hybird OTM Tactical (BC G1 .719 G7 .368).
I use to think I could do no better then the 200 Gr SMK in my 300 WM Model 70 1000 yard gun, but I've been working with Berger's 190 VLD and its showing promise in my gun.
Of course all guns are different.