Perhaps a jaunt throught the early chapters of Gregor Woods' Rifles for Africa is in order. The giant blackpowder gauge rifles went out of favor because they didn't work. Too many elephant, etc. were shot with them and went off to die of their wounds. Eight bore breechloaders with hardened cylindroconoidal bullets were better but when smokeless came out only the most reactionary pukka-sahib stuck with the old style. Check the documentation.