From owning the HE kit for years I have to say it’s definitely not pot metal. You can gouge pot metal with near enough anything. I am pretty sure it’s steel but also can’t find any official info since that Arnie thread.
You can go to Vegas and fire the real thing for about 30 dollars per round. I did it last summer during a road trip on the west coast. I don’t get why that’s not very believable.