I have one of each and like um all, but I think the Uberti 1858 chambers take a .454" ball, Pietta take .452" same with ASP.
If I remember correctly, Euroarms recommends .454 balls in their 1858s. However, since my other .44 cap and ball piece is a Ruger Old Army, I stock .457s. That's what I shot in the 1858 and they worked very well. No problem seating them and accuracy was good.
One thing that I thought was interesting with my Euroarms is that the chamber mouths came chamfered from the factory, something I haven't seen on any other cap and ball sixgun.