When I started working on the gong target I knew that I had two different steel types to work with. Some locally produced 13/16th mild steel plate and some AR500 steel gongs made by Quality Targets. This morning was the first chance I've gotten to hang them side-by-side and the difference in the two is interesting. First, the commercial target is a lot lighter, mainly because it's made of thinner steel. They both "whack" satisfactorily, but the thinner targets seem to be tougher on the strapping I used to hang them. Maybe something about the transfer of momentum when the bullet smacks the gong, but the heavier mild-steel target seemed to be easier on the hanging straps. Both of these are 9" diameter gongs.
Still, the difference is easily seen. First the mild-steel target, shot with a variety of deer-rifle calibers at about 150 yards.
Another interesting tidbit is that at the end of the day, the bolts holding the steel to the strapping were loose, way loose. What loosened those bolts? Maybe the shock of the impact? Heck, I don't know. They're tight again, farmer-tight.