Have you tried working up to 46 grains? In RP brass with CCI 200 primers that's been the really sweet spot for me with 165s in several rifles.
I did try 46 grains but accuracy started to slip. I'm not too concerned, I'm happy with the speed and accuracy I'm getting. This is, after all, just a single shot Ruger that will never be used as anything but a hunting rifle.
