Even though it says its #4 buck, its not. It is 5 pellets between #0 and #1 buck (pellets are .315 diameter, but 5 weight about half an ounce like #1 buck).
These are berdan primed, so they are not reloadable, and the cases are brass plated steel. I've seen sources for cases, but I have no load data for how they would be loaded.