to answer reincarnated's question.  I have seen a 45-70.

I posted a few years back about a 45-70 single shot sporter I saw at a gun shop in Phoenix.  It had a plate at the top of the magazine welded or brazed to help channel the round into the chamber.  It was fairly nicely done $800 asking.

If someone is interested I will spend some time on Google and figure out which shop I saw it at.  My post was in November of 2015.