[altaberg]

the example of shooting into a water-filled jug is irrelevant.

You can take a wooden box, milk jug, tank... and fill it with air or sand and shoot into it. You will get holes and a channel.
You take the same container, fill it with water and seal it and shoot into it; the entire container will be blown apart. It's a common first year physics experiment.

It's relevant only in the case of somebody being shot into a full bladder. The military and old soldiers know about that, it has happened and it is awful.