According to Buffalo Bore hardcast will not harm a polygonal barrel. I have not tried it myself as I have been using a Lone Wolf barrel when I shoot hardcast.
Here is the link.
https://www.buffalobore.com/index.php?l=product_list&c=59I have been pleased with my G20 scatching my 10mm itch, but if your heart is partially with something else, save your pennies and get what you really want.
