Mike,
I have seen the accuracy of a specific bullet change enormously with a change in powder, and also seen the accuracy of a given bullet/powder combination change enormously with a change in primer. But have decided the case doesn't matter much IF it's dimensionally consistent, especially neck thickness.
Have used a bunch of bullets to hunt various kinds of animals from small varmints to 1500-pound big game, and have my preferences. But generally I don't try to "force" a rifle to shoot a particular bullet well, partly because there are so many good alternatives these days.
But I also get to test far more different bullets than the average hunter, and usually have plenty of options on hand--which is why my big game load development often starts with a less-expensive bullet I know should shoot well, such as a Hornady Spire Point or Sierra GameKing, of about the same weight as the "premium" bullet I plan to use. Once I determine what powder and charges the Hornady or Sierra shoots best with, I switch to the more expensive bullet. Most of the time that works--and I end up with both a sight-in/practice/"deer" load and a load for bigger game, which usually shoot to the same place at 100 yards.
I used MD’s advice years ago with my Sako 338 and it worked wonders. 225 grain North Forks were my chosen bullet to be used on elk. He was kind enough to suggest a 225 grain Hornady spire point and it was quickly evident that the rifle loved RL-19. When I arrived at the powder weight the Sako preferred, I loaded NF’s. Same point of impact and velocity was a close match as well. 0.4” four shot group from the NF’s. Ain’t messed with the load recipe from that point forward.
