What is a barreling machine? It is the same thing some call a tumbler.

They are normally used for tumbling rocks which used different grades of sand to clean and polish the rocks.

This method will mechanically scrub your coins and is bad for items made from precious metal because it actually removes the surface metal in places. Of course that depends on how long you tumble them.

Dont put in coins that you consider valuable.

They work well for cleaning up any of your “junk” coins though.