The voltage is read back via a 1M/10k divider until 200 volts is reached. Then the SCR (mislabeled triac above) is fired and 200 volts applied to the primary of the ignition coil. Note, the 12 volt zener is needed to let the capacitor discharge to zero and allow the SCR to reset.
The resulting spark is about 1/2 inch to a spark plug with a modified gap.
Most of the
electronics and momentary switch are located in the handle.
Coating the marshmallows with flour keeps them from sticking in the barrel and improves performance. Watch out when they get a bit stale, they really come flying out then and may go several hundred feet.
Don't forget to 'air out' the chamber between firings, or you won't get any real action.