What fun! - The reason for long cases, underloaded to reduce pressure is for double rifles of the day that didn't like 55,000PSI. Cordite greatly increases pressure in hot climates, another reason for out-sized cases. I notice there are several doubles now chambered for high pressure rounds ie: .458's and .375's, .30/06, etc. All of these produce higher pressure than the hot-rodded .45/70's. I don't see pressure as being a valid point - maybe back in 1920, but not now.
; Would I take a Marlin to Africa - bloody not. I've a great .375/06IMP that exceeds original H&H ballistics and can easliy re-chamber any .45 to another nice '.458 Alaskan' (rebated rim .450 Alaskan on a bolt-gun) that easily does 2,200fps with 500's as it has slightly greater capacity than a .458 WM. It will probably do 2,250fps, but it's already faster and penetrates more deeply than most of the Nitros. Yeah, I know it's blasphemy to say things like that - sometimes the truth hurts.
; The truth of the matter, is that the hot-rodded .45/70 puts out ballistics that 'could' be effective and so far seems to have been effective, on some species African dangerous game. Remember one of John Taylor's favourites? - a single shot .577/450. That's shot a 480gr. lead, paper patched bullet at about 1,380fps.