I currently have a White, Model 97 which is a .504 Caliber. Any recommendations on your favorite and/or most accurate load for it?

I shoot the 480 gr "Super Slugs" & 480 gr "Power punch" Bullets backed by 90 gr of pyrodex p fired by RWS caps.

awesome, thank you, Leemar!

Yes, any powder but pyrodex including real black powder. I started using it in 77 when it came out and still have a few pounds of it, which I will give anyone who comes and picks it up.
It is the worst BP substitute invented for several reasons.
And it killed the inventor.
I use 100 grains of 777 with 45 cal sabots; but for more power, use the solid lead bullets like lee said.

Swiss fff 75grains with 460 grain bullet.