My target is a 500 brinell armor protector plate. It basically means that as long as the terminal speed is less than 3200 fps, you can shoot it all day long.
Also, My target has a bolt on clasp instead of a chain. I think chains can break after getting hit one or two times.
go to www.metaltargets.com
I am very happy with mine. You can also interchange the gongs. I have a 15" and will get an 8" soon.
If you can tell from photo, after being hit, the only thing done to target is the paint is chipped off. No dents or pocks. All you have to do is spray paint over it.