The rifle cost me twenty dollars and was rusted to hell when I got it. I have allready spent more on the rifle in EvaoRust than the gun is worth. I have tried sabots with it before with terrible results. Round balls did no better. My only other option was to try some big lead. I thought that they shot pretty well considering the shape of the bore.
I'm also not aware of a saboted bullet being a good choice for a 1 in 48 inch twist barrel. Let alone a badly pitted one.