Dave Canterbury shows how-to in this in-depth video. Would definitely make a general purpose survival black powder weapon with out all the hassle of cleaning conventional muzzleloaders.<iframe src="http://www.youtube.com/embed/ES59LtA7XE8" allowfullscreen="" frameborder="0" height="315" width="560"></iframe>
Why would you not just reload the shotgun shell with the same materials and retain the convenience and speed of breech loading and easy reload with the next shell?
Just another way to utilize this very versatile weapon in a true survival situation. Besides, I have walked past hundreds of old shotshells just laying on the ground with the plastic hulls damaged beyond being usable. Just another way to get from point A to point B.
Guys around here use about 5grains of black powder to their reloads of 12ga. for turkey hunting so they can get a little more distance out of them.