FBI standard is 12 inches of penetration. 2" of water equals 1" of ballistic gellatin. That means 4 milk jugs worth of penetration. I think the Feebs are a bit paranoid after the Miami shootings and I'll setlle for six, but that still means blowing up the third jug, even if the shot doesn't exit. I'm not confident birdshot will do it, though in an apartment situation I'd settle for that because the only thing worse than getting killed is killing an innocent by mistake.
FQ13