I've been corresponding with Charles on this topic - I didn't see the thread.
; Either #3 or #4 will easily handle .45/70 or .45/90 at lever-gun ballistics - ie: 400gr. at 2,100fps. If one wants to soup things up a bit, the #4 will handle the same pressure as factory loaded .458 mag, easily. With a nominal leade of 3/10", this would result in ballistics equating the .458 mag. due to bullets being seated out or allowed to jump.
: I would never consider re-boring a slender military barrel for a .375 or .458 cal. rifle when much better barrels are easily aquired from PacNor, etc. It may be OK in .375, but still wouldn't do it.
: Any of the smaller wildcat .375's wold work beautifully. magazine work may have to be done, of course. Single stack on larger rimmed cases, but my #4 feeds my .312 Express (Waters) just fine(.350 Rem. brass). I only put in 3.