My thoughts on the .350 Rigby are - use it with the 225 grain bullet and enjoy the classic load. It worked well enough for Taylor, Bell and the others. It's the same bullet weight as the standard .338 Winchester Magnum load (though now one sees 200 grain bullets in the .338), which means the sectional density is a little lacking compared to the .338. So what? The .350 cartridge (and the rifle) are beautiful to look at and it will kill as effectively as the .338 in most situations.

If one needs a 310 grain bullet with better penetration and SD, how about the Rigby .400/350?