If you don't reload,buy 1 box of every different load you can find,shoot from dead solid rest,compare groups.
If you do reload then try about all the different combos same as above. H110 is my "go to" powder for full house magnum handgun loads. There are plenty of other powders out there and I've tried most of them but H110 can't be beat in my book. I'm sure it's not the revolver's fault as I've never seen a truly bad ruger yet.