I shoot a Gustav Genschow 500 x 3.25 clamshell action
load is
Primer Federal magnum
ADI 2208 ( Vargent) 80 grns
5 grns Dacron filler
440 grn woodliegh SP
doing 1935 fps
I've been shooting this load for about 12 years and it works well for me

all the best