Look through here Im sure someone has plans

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I expect to see a bullet fly through my window and right into my chest any minute now.

Wow... sounds like you have a problem...

Well on how to build the cannon look HERE You will see a lot of how-to's on there. If you look at the how to on propane injection it is a very good writeup. There ...

Yes voltage sorry... but the gap would be very small, almost impossible to create without touching.

And you could rig something to strike the contacts, like get an old R/C car remote and servo. Put a piece of metal on it, and when you move the servo, bam! remote firing!

The only way to fire it in the comb. chamber is mechanicly strike the two contacts with a piece of metal.

BTW... What Shandora is talking about is there is not enough amperage in a camera cap to jump a gap. A taser is built a little diff.