No expert here but have shot at an AR500 target from 7 yards with 9mm jacketed bullets quite often. I think I managed not to get hit because my mounting setup angles the target toward the ground slightly and the hard AR500 doesn't crater. Bullets hitting craters will splatter in uncontrollable ways.
Long time ago, early 80's, we used to shoot .357 and .44 Magnums at soft steel targets from 50 yards away which would get pretty cratered and we would occasionally get hit by fragments. Not hard enough to break skin or even hurt but you knew you were hit by something.
So I wouldn't recommend shooting the soft steel targets from up close even with milder rounds.
You want your steel angled at 22 degrees, or a lot further away.
