A working 1/72 scale cannon especially made from that kit is smaller than I thought possible - please provide details of how you did it.
The smallest one I made was akin to a .22 and used Black Powder. The thing would jump violently and I would be terrified when igniting the fuse.
The problems I had were with powder had initially used my own home made gunpowder but it caked badly and would not ignite when in small amounts so when I had a friend give me some black powder that worked a treat. The other problem was the fuse being small enough especially given the size of the hole to access the powder charge, eventually I had to make the hole larger than what was in scale with the model.
Anyway it could fire a small ball bearing deep into a water melon at 3 metres so I was happy with the results... What ammunition if any are you using?