Marrakai:
Great addition to this post. Sort of looks like the old upside down .38 full wadcutter approach.
nasty expansion. I imagine velocity wasn't much of an issue here. Likely, in .455, to deliver more felt impact at these 700 fps velocities than modern rounds at higher!
I use 255gr flat nose swaged lead in mine. I am more into hitting something like a large boar as an outside chance target.