IIRC, the 284 case water capacity is 66 grains and the 7 SAUM's is ~ 73 grains. In my 284 with a 23" tube I get a smooth 3100 fps with a 140 and a max 52.5 grains of R 17. I would think you could start there or a grain higher, and work up if there is room at a .5 grain at a time.
I presume you'd be safe starting at my max and working up.
