I watched a Mythbusters episode six times today. It included a section on a cannon made out of a log. In the episode, they made their own gun powder. For those of you who want to do this as well, here is the formula.
By volume, not weight, mix together:
75% Potassium nitrate, 15% Charcoal, 10% Sulphur
add enough water to make a paste, and mix well. Let the mixture air dry. Using a non-conductive mortar and pestil (made of brass, or hardwood for example), grind the dryed paste into a powder. Finer grains are better for some applications. For a cannon, larger chunks (possibly as big as the first joint on your finger) are fine. Store in a non-conductive media, preferrably somewhere outside your house. :o)
Please don't play around with this mixture. This stuff is volatile! A single spark can turn this from powder to explosion! However, that said, in the right hands this is a way to create a means to power a muzzleloading rifle, and obtain food.
I don't feel bad posting this, since most people could find this on the internet as easily as I did if they wished. I also researched how to make Potassium Nitrate and charcoal if anyone is interested. Finding the sulpur could be a little more difficult. :o)
Have a nice day, and work responsibly. Stick.