Let's look at some rifle rounds.
These were the first Dum-Dum bullets.

I took a standard .30-06 Military ball, 150 grain bullet and used a hack saw to cut off the nose of the bullet and expose the lead inside. I then used a Dremel tool to smooth-up the surface.

Just a word of caution…

Any time you are shooting a round that is "open" on both ends, there is a possibility of the lead leaving the weapon and the jacket getting stuck in the rifling.
Always be sure to check the bore for obstructions before the next shot.

Let's see how it works against the water jugs.

Here I am shooting it out of my 1903-A3 Springfield.

Water rained down all over me.

It busted the Waterbox all up.

It busted 4 jugs and came to pieces, shedding the jacket..

And a closer look.