Potato Cannon Design

Components:
  (1) 4" Clean-out cap (threaded)
  (2) 4" Threaded end thingy
  (3) 4" diameter x 2' long ABS pipe
      combustion chamber
  (4) 4" with 2" sticky out bit
  (5) Reducer - 4" to 2"
  (6) 2" End cap (sealed)
  (7) 2" diameter x 4" long pipe
      acts has handle, when inserted in (4)
  (8) 2" diameter x 2' long pipe
      barrel of the gun
  (9) Igniter
      Universal barbeque lighter
 (10) Sparker
      Universal barbeque lighter
      Mounts in two holes (a) drilled in (4)