We made one out of some abs pipe at my station. Set it up with a flint sparker and it worked like a charm... turns out though, that if you fill the space up behind the potato with 100% o2, you can just go bat**** crazy with the amount of fuel you use and it adds a whole new level of bang to your potato gun.
Oh heck yeah! the good old days.......we would fill it up with Aqua Net.......for some reason has to be Aqua Net hairspray(ha ha ha)and let it rip.
We put a hole right thru the neighbors fence.....not good........
All hail the great Spudzoka! Destyroyer of fences, Hwy. bill boards,and any other flimsey built targets.
Back in the early 1990's we built a couple of spudzokas out of ABS pipe and used a push button igniter from an old gas BBQ to lite off the WD-40 used for propellant.
We built a fairly good size chamber for the propellant which created a pretty good muzzel velocity and this thing would shread on old abandoned plywood backed Hwy. road sign at distances just short of 75 yards.
One note on propellant: WD-40 works real good and so does Aquenet hair spray. Either worked but not quite as well as the WD40 or hairspray. Also loading the combustion chamber with alot of propellant is no good. You just need a little bit to get the best results. Something about having a good amout of oxygen to go with the propellant to get that real good BANG.
White and red potatoes work but if you really want that special potaote projectile that tears things up the Idaho Russet potatoe works the best.