I have been shooting my Chapuis 470 for the last couple weeks working on loads and consistency. I leave tomorrow for the Dark Continent and an appointment with a Cape buffalo.
Mine seems to digest almost everything I throw at it well. Both barrels stay inside of 3 1/2" at 50 yds with several different loads and bullets, if I do my part.
I have settled on 500gr TSX's pushed by 82.5 gr of Reloader 15.5 and a Trader Keith foam wad. Again, if I do my part, they will regulate at less than an inch with them often touching. Speed is right at 2075fps.
I am also taking a few CEB solids pushed by 83gr of 15.5 that groups close enough to give me no worries.
4831 and 4831SC shot very well too, with slightly more speed, but much more recoil due to the increased amount of powder.
Good luck and enjoy a fine rifle.
P.S. JJ Perodoux recommended 79gr of 3031 for a starting point as well.
And as always, start low and work your way up. What is safe for me, may not work for you.