I like the 50-90 and stuff in that range, also any of the British BP Express cartridge rifles. A buddy has a Martini sporter in 577/500 Express and it seems like it would be a tremendous rifle for the purpose. Certainly the 45-70 needs mention as it is so easy to find the cases, bullet moulds and such to load them, even if it is a bit on the light side when loaded with black, but still not too bad if ranges are kept reasonable.