Some foundation load information FWIW

I found some of my old loads for Trail Boss and cast bullets for an idea where to begin. They are volumetric correct as Trail Boss has a little unique loading character, you don't want too much air space, but don't compress/pack it.

My .416 GNR and 300/375 gr. cast which would be in the ball park for others such as .440,.450, .475 GNR is 20.0 grs and a magnum rifle primer. It garnered in the .416 from a 13+2" Encore 1250 and 1100 fps respectively.

The .476 GNR I got almost the exact same results from a 325 and 420 gr. cast bullet using that load.

For .470 Nitro Express and a 435 gr. .475" cast pistol bullet I used 33.0 gr. Trail Boss and got 1430 fps from a 22+2" carbine barrel. I even paper patched a .458/500 gr. bullet for use in the .470 NE but that is another story...

You can't hardly any data on that stuff anywhere but that will point you in a good direction.