Back before slugs were produced, people had to improvise a bit. What they came up with was a great way to use bird shot and make it operate as though it was a slug. Watch the video:
If you watched this to the end you can see how the entire hull shoots out the barrel and keeps the shot together until it comes in contact with the target. As it was explained in the video, you have essentially created a 70mm Glaser shell.
As you can probably imagine, these would fire best out of a break action shotgun and would probably not feed too well. I wonder if some tape would hold the shell together long enough to feed through a pump, but powder escaping the shell would be a concern.
I can definitely see this as a great self/bear defense round in a coach gun and now wonder if I should consider getting one for just this purpose. This is quite ingenious, however. Little tricks like this make me quite happy.