WARNING!: do not over fill with gunpowder. i would only use black-powder and a small amount at that. THIS HAS THE POTENTIAL TO BE A PIPE BOMB ! please stand no where near this when firing. if i were to take extra precautions i would pour molten aluminum down the barrel and drill a bore hole. have fun but not too much!
if you want to see all the videos look up "miniature hardware store cannon" on youtube