Loading info needed for 500 A square rifle with cast

[smoked turkey]

Need a starting place for loading for a 500 A square bolt gun. I am thinking of the Lyman 515142, 515 gr, sized to .512. I have no idea where to start. I have searched the internet for cast boolit loading info and so far I have come up blank. This boolit is unchecked and that will limit the velocity to 1700 fps (?). I figure if my son wants to drive it faster he can use J words. For me I only want to shoot cast as my old shoulders won't take the heavies with jacketed. Any help will be appreciated. Still need to find dies, a mold and sizer die so am still a ways from actually doing it. Just starting here for ideas. Thanks!