This is an extremely simple compressed air gadorade gun that can shoot a bottle cap 75+ feet. This project can be a fun and easy air cannon or a great prank that you can play on a friend. All that is required for this project is a gadorade bottle w/ cap, a air compressor/pump, and a ice pick or knife.
This gun makes a loud pop when fired and will surprise anyone nearby. Depending on the air pressure this gun can be a safe prank or a powerful air gun that is dangerous. A safe pressure to play a prank would be anywhere from 10-20 psi, but as a gun this should be fired at NO greater then 45 psi . At 70 psi or greater you are in danger of having the bottle explode and that would not be very pleasant.
This is a really fun project and the videos don't due it justice. You really have to try it out to understand, and besides it is free and easy!
First you take your ice pick (or any other sharp metal object) and heat the tip on the stove. When it is hot enough to melt plastic take it off and quickly poke a small hole in to the bottle at the place where your pointer finger naturally rests. This hole should be no bigger then the size of the ball pump needle you use to fill it.