I've actually thought about necking the .45-70 casing down to .338, myself, with a short and sharp shoulder angle for accuracy. I tried mocking it up at one point but I couldn't find any torrents for QuickLOAD, and I'm not paying $150 for that shit. Obviously that's not perfectly straight, but if you could do it it'd be a round that probably rivals most .30 caliber big game rounds, except it would fit in a short action.
If you were to put, say, a 160 grain .338 flat nose bullet atop a 33mm case (a tiny bit shorter than .44-40 Winchester, same length as .357 Magnum, a tiny bit longer than .44 Magnum), I'd imagine you could probably load it to 1800 ft/s while keeping the pressure reasonable (below 35k psi). People can get loads out of .44-40 as hot as 200/2000 in rifles, so I'd expect good results… however, at that case length I think it'd probably be pointless, being so close to a lot of other revolver cartridges, so I might use a 36 or even 40mm case just to differentiate it and make it stronger. At that point it'd be competing with .454 Casull and .500 Smith & Wesson, and you could probably argue for it as a lighter-recoiling but slightly less powerful option than those.