In my 450/400 3 1/4" I use 81grains of IMR 4831 with 400 grain Woodleighs Softs.[Federal 215 primers, no filler] 83 grains shoots good in my rifle too but 82 grains does not.
My rifle also shoots good with 71.5 grains of RL15, Federal 215 primer and a foam filler.
After further tests I hope to switch totally to RL 15.