Further reason to stick to my .450 Nitro Express instead of trying to use a 4 bore Smoothbore on those brutesan interesting part of this discussion is the need to harden projectiles in order to get anything like penetration.
today, the commonest way to harden lead bullets is by adding tin.
the max hardness that can be obtained with tin added is 1 part tin to 10 parts lead.
to go harder you need to add antimony, but this cannot alloy with lead unless ton is also present.
the problem with antimony is that the harder the bullet gets, the more inclined it is to shatter on striking a target.
this could be signing your own death warrant on dangerous game.
the victorians used mercury added to lead to harden it, but who wants to do that!
hardened conical bullets would be a given for dangerous game, which means a rifled barrel.