I was thinking about making the 30mm cannons simulate rapid fire, using a movie prop trick with LPG, a combustion chamber, solenoid ignition and steel pipe in the centre of my turned wooden cannons. Mechanically, I can do this fairly easily, I have all the tools, materials and resources to make it happen. Legally, knowing what this nanny state of Australia is like, I wonder if there is a way to get a permit? Is there some condition or waiver available for something like this? Are there any plans, schematics, or simple mechanical examples of this I can investigate? Baz.