Re: powders for .243 and 90+ grain bullet
I shoot 90 Bergers or Accubonds over Superformance for velocity superior to other powders. I get an instrumental (12 feet) 3360 to 3380 with 48.0 to 48.7 gr. I use HBN coated bullets so I need more powder to get the same pressure.
I have tried 100-V, VV N550, N-560, Ramshot Hunter, Reloader 17 and Reloader 22, H4350 and H4831. The sweet spot is between 4350 and 4831 in burn rate for this case volume and bullet weight. Quickload shows this. Hodgdons data also shows how Superformance is the best choice. They even show a load on the label for .243 with amazing velocity.
The worst piece of advice is H-1000. Quickload shows that you will blow a lot of it out the end of the barrel. It might be exciting for night shooting or fire starting.