darnit, i forgot to add this, this will make the best mod for a potato launcher ever, it will mainly appeal to those of us who own small potato launchers, not huge massive things like yours, but rather , luanchers that would be more suitably called air rifles. as in guns you can use to shoot at your friends without decapitating them, like mine which's combustionchamber has a volume of 2.5L.
anyway, the problem we often have with the smaller potato launchers is that its easy to overdo the air to fuel ratio, if theres not enough, it wont burn, if its slightly too much, it will just make slow flame inside the launcher, if theres WAY! too much then it wont go at all. but get it just right, then BOOOOM!!!, gunshot loud, like any normal launcher.

my point to this long post is that you should perhaps build a mod for a fuel injector, for the spud gun, it would work in the same principles as a standard inhaler gas cartridge, which lets out only a certain amount of gas in one squirt, no matter how slowly you push it down, that gas released will not flow contantly, only a specific amount will come out.
if you can build something that delivers a specific amount of gas on each go, then people will be able to get a perfect air fuel ratio each fire,(balanced combustion), and they will be able to get the most out of their mini potato launchers.
having sid that ill remind you some peoplelike me have parents who do not allow large dangerous spud cannons, that can kill. you may be able to for whatever ewasopn (dont live with parents, or live with parents who couldnt care less). people like me can only own small ones, but the mod should work for all potato guns.
i dont know if it matters how long you spray in for in yours , but in mine, any more than 1 sec is too much.

i made the silencer and i gotta warn you guys, DO NOT MAKE IT WITHOUT USING A DRILL , take it from me , personal experience, if you use something sharp or hot, to peirce a hole in the pvc pipe, it will make something like a mole hill inside, this will cause your ammo to get stuck inside the silencer, which is quit easy considering that its where the pressure is released.

 dude, how did you make the silencer?? that looks awesome! i want to add that to mine :) hahaa silent, but deadly :P

Never too many for spud guns! I want! Needless to say, I may not make them, but I am interested in the ideas.

...make the instructible ANYWAY! the more the merrier!