.I started off taking apart one of those big air powered streamer things that you get at firework stands around the 4th. This would be my combustion tank. I then took apart a grill lighter and saved the piezo electric igniter, and the nipple that connected the lighter in the handle, to the tip of the lighter. I also needed a 3/4" pvc end cap and threads, and finally a Bic pen for the barrel and ramrod.
I took my Dremel tool and cut a hole in the end for me to epoxy my cap and threads. I also used it to drill into the side for the ignition points, and butane nipple.
I then epoxied the igniter and wires for the ignition point onto the side of the tank, along with the nipple.
As for the barrel I took and cut off the narrow end and filed the edges to a point, and put electrical tape on the end to wedge it in the tank.
After that was completed I had my gun to shoot paper and potatoes.
I later made a dart out of sharpening a nail to a point and wrapping tape around the end to make a seal. Works great!
you can see here the assembled gun, ramrod, and dart
This is the gun all taken apart
This is the gun with everything in it, including a cigarette lighter
Here is the inside of the tank, you can see the ignition points on the left and the butane nipple on the right
Todd
.Anyway, thats a nice mini i like it. It has style and it looks awesome. BTW, have you ever been zapped by the wires on the outside? (i have. 
).