I just don't think that a very high-powered autoloader makes sense. My thought is that the purpose of having an autoloader is that you can shoot multiple shots, and reload with ease.
When it comes to very high-powered pistol rounds, there is rarely a need to shoot that many times, thus a revolver would make more sense, and would be better built handle a stout recoil from high-powered pistol rounds such as 454, 460, 480, 500 and the like.
If you were hunting a big game that can kill you and somehow have to empty all 6 shots in the cylinder, that would be a bad day....
Agree with everyone above about 7.62x39 or 223 not being a great big game hunting pistol. There are 7.62x39 "pistols" or "stockless rifles", but I'm not very clear about its niche, as I'm not sure about the use of 50AE Desert Eagle either.