Walter Bell settled on the .318 WR as his elephant rifle around 1909/10 and used one of them thereafter. Despite his fame with the 7x57, he moved to the .318 and that is the chambering he recommended in his books, with a 250 grain solid. (That and the 8x557 Mauser)

I always wanted one and I have a .30/06 and a 9.3x62, in the same spirit of things, but never have seen a .318 for sale. I cant find anyone who makes a .330 bore barrel or a reamer in NZ or I would build one.