The build of my potato cannon in video form.

Step 1: Build List

Pipes

3/4" t fitting x1

3/4" right angle x2

3/4" male to male short x5

3/4" male to male long x1

3/4" to 1/4" x1

3/4" ball valve

3/4" sprinkler valve

1/4" male to male x1

1/4" air compressor valve

Barrel

What ever works

Tank

20lb propane has a 3/4" output once the valve is taken off

Solenoid

3/4" Sprinkler valve fired using 9 volt battery

All parts should be fine at 120 psi but I am not responsible for anything you do with this build list.

Air Powered Potato Cannon From 20lb Propane Tank