I shoot 6mm Remingtons that are 9" twist, but the Bergers should shoot very well in your .243. With a max load of 49.0 H4350, I shot 5 in .167 from my H-S barreled 40-X. That load averaged 3570 fps. Five 5-shot groups averaged .389. Everyone I know, including me, that has used the Berger 80 MV on coyotes swears by them. Good choice.
The attached QuickLOAD PDF shows 44 RL17 at 3300. It is very likely a MAX load. Please reduce to 40 and go up in .4 increments.