RE: 243 100 grain Nos partition
I have generally gotten the 95 grainers to shoot a little better out of true 10" twist barrels. All the new Remingtons have 9.2" twists, so they may shoot the 100 gr. bullet bettter. You'll probably just have to try them and see. The difference in velocity or terminal performance will be minimal.
Another bullet definitely worth trying is the 100 gr. Sierra Pro Hunter (flat base design). One of the all-around-does-just-about-everything-well kind of bullets in this caliber. Has also proven to be accurate in just about every rifle of this caliber I have tried.