Commonly known as "zip" guns, a pipe gun is made from pipe and have been used for years by juvenile punks.
They can be used many times but with some, a length of dowel is needed to force out the spent shell.
There are many variations and this guidebook details construction of the most straight forward design.
To fire, the trigger is pulled back with the left hand and held back with the thumb of the right hand.
Firing mechanism of a homemade pipe or zip gun is the same as that for the pistol. It naturally has a longer stock and its handle is lengthened into a rifle butt.
When you make a zip gun, you should test it before firing it.
This guide all the details for getting started, from materials needed, the construction process, to tips and a diagram of the basic design.