Sarg - I saw one a while back ('Rifle' Magazine, I think), converted to the .45 2.4" case (Winchester .45/90).

That one, in a #4 Enfield could run very close to .458 Win Mag ballistics - ie: 2,250fps with 400gr. softs or solids.

The triple 4's and .405Win., while not quite as powerful as the .45 cases, would also be good choices.