This is the setup.
The box has 12 gallons of water in a row.
If the rifle rounds penetrate more that
that (about 7 feet), then we will be out
One problem we will face is trying to get
the rifle lined-up so that the bullets stay
in the middle of the box.
But we found that the bullets sometimes
deviated from a straight path and this caused
some problems, as we will see.