Have you also tried RL-22 or RL-26?
Your case size can use both of those powders extremely efficiently, plus you'll see higher velocities, with lower pressure curves.
H4350 is also a go to powder that will work well in your case, and caliber.
RL-26 & RL-22 are meant to be rifle Magnum powders.
Your case capacity is the same as my .280 Rem, and I'm going to use both of those powders to eek out every little bit of velocity I have in my 24 inch barrel T/C Venture .280 Rem.
I can safely get a 140 gr bullet going in the mid 3200 fps range.
With both of our cases, they're roomy enough to use the slower burning powders and get as much velocity as one can get.