You are talking some big boys there. I could be wrong on this, but I think the pressure on the breech face would be too much with those you mentioned. I am not sure on the 9.3X62, but I know the belted magnums are out. Maybe a 375 Win or a 35 bore of some kind, just thinkin', but kinda tame when compared to the 45-70 when loaded up. You will have to get it bored and re-rifled of course. I do not think a stub project would be a good idea with any high intensity stuff.