I typically save old milk jugs, fill them with water, take them out to the range, and line them up.
Shooting into water gives a "best case" scenario as far as expansion. Put some old jeans in front to see how much of a problem plugging is. IIRC bullets will penetrate about twice as far in water as they will in tissue/gel, but I could be wrong.
I don't carry a gun to go looking for trouble, I carry a gun in case trouble finds me.