I planned on using like 4 9v batteries...

i used bbq last time with same chamber, and had to click it so many times to get a good enough spark

I truly do not have a set design yet. I only know what aspects I want the cannon to have. These include:
Propane injection system
Car ignition coil
Detachable barrels
Safe

Does anyone have any experience with using this to ignite your cannon? Are there any risks in using it in this fashion?

Alrighty, thanks!

I am wanting to make a single shot, shotgun style function for the spud gun I am planning. It will have detachable barrels, likely including 2" and 2.5" barrels, along with a 3" expansion chamber. It will use propane for fuel. I would like to make a barrel/attachment for this, so I can shoot somewha...