You'll have to find you own best load, I'd recommend the 95gr-100gr first, far more 243 H&Rs have been reported to shoot them better than the lighter bullets, I have three 243s, a Superlight that shoots 100gr Speer handloads(Stimpy's H4895 load) very well for the first couple shots, almost touching at 100yds, the 3rd opens the group up to 1½-2" if shot quickly. The other two are 24" Ultras, they also like heavy bullets, the 95gr Fusion and 100gr Power-shoks both shoot 1" or less, and those two factory rounds are probably the most popular factory 243 loads, along with the Win Supreme 95gr Ballistic Silvertips. Mitchell's 243 Ultra shoots handloaded 55gr and 95gr Ballistic Silvertips under ½", same for the factory 95gr Win ammo.
Some have been happy with the 85gr Federal Permium ammo and 80gr Rem Core-lokts, the 80gr Rems shoot fair in one of my Ultras, but are poor in the other and the Superlight.
Howard NZ shoots handloaded 100gr SSTs in his Superlight, he's killed a bunch of deer sized game with it in New Zealand.

So be sure to be open minded when you're looking for a load, specially for the Superlight.

Tim