How thick is the plate ? AR500 rings nicely when hit if hung properly , from the description it sounds like it was . 3/8 inch plate is enough that far out , the thicker the plate is the less it rings but you still get the smack when hit .
The problem with the thinner plates and mild steel even at those distances is the steel gets dished pretty fast . Dished plates can send rounds in weird directions because of the curve . Reversing the plate to shoot The dish out will cause the plate to crack .
With practice you can tell the difference between splash on steel from the bullet and dirt getting kicked up on a miss by eye .