Steel shot had a LOT of development to make it soft enough to shoot in most new guns. Steel BB's ball and ball bearings are way to hard for a gun barrel. Steel buck shot would be a ballistic disadvantage also as it is too light to carry the penetration you need. Yes folks have tried all of these options and I have got to see and try and repair the end results. On older barrels even REAL steel shot can bunch up and bulge a barrel especially if you don't use a special steel shot wad.

If you really want to try this please keep me in mind for the ruined barrel as I donate them to Hunter Safety teachers.