Let's discuss spud guns. I'll make a small guide on how a spud gun should be made.
http://www.burntlatke.com/
Materials - Pressure rated pvc ONLY. ABS makes shrapnal and fails easier then pvc. Use pvc primer and cement ONLY. Let it sit overnight before firing. I recommend 1.5" for the barrell and 4" for the chamber, although I've used 3" and it works. I like 4" better though.
When designing, make sure to make a gun with the correct C:B ratio. (Chamber:Barrell) If the Chamber is too big then the shot will be loud and there will be wasted energy. If the barrell is too big then the shot will be quiet, but friction and suction will slow down the spud.
C:B calculator -
http://www.burntlatke.com/ratcalc.html
C:B graph. This is using propane, and the optimum C:B ratio is .5:1 to .9:1. I think .8:1 is the accepted best overall ratio, and I use about a .7:1 so it's a little quieter in the city.
C:BGraph
For fuel, the best were found to be propane (metered) and the best aerosol is aerosol starter fluid. When using propane, you could take a torch and squirt some in without measuring it, but the educated way is to use a
propane meter.
Ignition - The old BBQ ignitor works, but a stun gun is a wonderful investment. You will also want to look at a flint sparker for a lantern too. Check out the
Sparker Reference Guide I've found another ignitor too -
http://ultimatespudgun.com/product_i...roducts_id=219
I've bought two $16.19 shipped stun guns off of ebay. They work great and provide a large, helthy spark. They're called "STREETWISE STUN GUN". I looked now and found one for under $16 shipped. Just a heads up you'll have to open it up and disable the alarm because it a loud mofo.
Chamber fan - this is optional, but it vents exhaust gasses and circulates the fuel better, providing a better ignition.
So things to consider are ignition system, fuel system, chamber fan, and maybe a handle/trigger. I'm so bored, I'll post a link to the tazer review I took pictures for after I write it.