I often thought that a flanged 318 WR would have been nice but then there was the ?? 303 Axite ?? which was very close to it & of that didn't cover it the 333 Flanged Jeffery probably did. As for the 470/416, I really think the 450/400 ballisticly covers that one too, if you want more oomph than that you're right into 500/416 territory with the accompanying recoil. Not a lot of free lunches to be had by the look of it.
Steve