RL-7 in mineI've used both RL-7 and AA2200 with good results.
I have slowly changed all my loads to CCI450's because 400's were not holding up. plus It's one less primmer to have on hand.I have had good luck with H335, rem 7-1/2 and 32 vmax in my cooper 38. 21.8gr gets me about 3700fps. Remington brass. I do notice that hot days on prairie dog fields do increase pressure a bit. That load was too hot for cci 400.