Tis a very North American viewpoint stated so far. Having recently returned from New Zealand where I heard the statement "the .303 has accounted for more head of African game than any other cartridge & possibly more than all the others combined" I think I hear what your saying. I would agree with the earlier posters saying its not for the big 5, but also think it is capable of larger animals, up to say Eland. A good solid would be a nice choice were you to be wanting deep penatration. I cant say I know a source of them. I have a .303 on a small frame Gibbs Farkey, great round still today.
Steve