Combustion powered spudguns have four basic elements:
In order to fire, the operator loads a projectile (usually a potato) into the barrel, adds fuel to the combustion chamber (for example aerosols or propane), and triggers the ignition source (e.g. a piezoelectric BBQ ignitor). The fuel should then ignite, create hot expanding gases, and force the projectile out of the barrel. Distances vary greatly depending on the type of fuel used, the size of the launcher, and the "idealness" of the fuel/air mixture; 100 metres is a common distance.
High tech combustion launchers may now include metered propane injection, chamber fans, multiple spark gaps (spark strips), and high voltage ignition sources (flyback circuits, stun guns, camera flashes, etc). Combustion launchers are mechanically simple, but are weaker in typical situations compared to a pneumatic launcher of the same size. Potato guns are often painted to increase their aesthetic value and to cover unsightly primer stains. Krylon Fusion, a type of paint specifically made for plastics, is the most common type of spray paint used on potato cannons.