A simple potato-pellet firing air rifle made from stuff that you can usually find in the shed...
This gun fires pellets cut from potatos, and is more or less accurate at 30 metres. It has a pressure chamber made a domestic waste piping bottle trap, and is filled using a valve from a bicycle inner tube. It has a trigger made from a washing machine stop valve, and a barrel from 15mm copper piping. It's put together with standard plumbing connections, and bolstered with a liberal amount of hot glue, and tape.
This video gives an overview of the finished potato rifle and shows it firing.
The rest of the Instructable takes you through the steps to make it - enjoy!
Step 2: Pressure valve
This uses a normal bike valve. Cut it out from any old inner tube that has been lying about in the garden. It's pushed through a hole drilled in a standard end plug and then sealed with hot glue.
Bicycle technology is awesome. It pre-dates, and was used to develop planes - fantastic!