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.
Mathman, what kinda velocities does that load give you. I went up to 45gr in Lapua brass, which gave me 2752fps. Accuracy was very poor, but 44.5 gave me just over .5", so the 45gr may be worth trying again.
John