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I'm presuming you're referring to using AR500 _targets_ in my ruminations below;
if the steel surface is pristine, and you're using lead bullets, you can probably get away with 5 yards for an extended number of rounds. if the steel surface has ANY irregularities, I'd say no. If you're shooting jacketed rounds, bounce back of jacket fragments can be unpredictable. Over +- two decades of monthly steel challenge competitions, I recall two instances of jacket fragments drawing blood (exposed skin) at 11 yards.