Charles Bronson if available should be able to help. He hand loaded for his and after he shot that bad guy you could see clear through him.
I just did a search on Google and there are numerous sites with data.
It is always better to get this info first hand, for safety reasons..good luck , and have fun.I like the lee load book.
Try reloadersnest.com It's free and many obscure calibers listed.From cartidges of the World...............475 Wildey magnum 250gr/21gr Blue Dot/1850fps/1900ft.lbs. 300gr/18gr Blue Dot/1610fps./1727ft.lbs. Harold