I have several gongs in 3/8" and 1/2" the 3/8"seems to hold up just as well as the 1/2". my supplier sells me Hardox 500, must be close to the AR500 guessing just a different manufacturer.
Hardox is a Swedish manufacturer, and is extremely highly regarded. Some steel suppliers consider it to be the best. Hardox 500 is the same grade of hardness as AR500-spec.
I’ve done some torture testing of 3/8” Hardox 500, and as long as you keep impact velocities below about 2800 fps, and avoid hard bullets like steel core, you’ll typically not even divot the steel.
