How to make a small pneumatic gun out of a pen. It can be pressurized over 100 psi and shoot small nails into wood. THIS IS DANGEROUS if you choose to make this I am in no way responsible if you injure your self shooting it or if it explodes while your pressurizing it.
*I didn't know this but someone has already done a better job of a pneumatic pen on spudfiles http://www.spudfiles.com/forums/pneumatic-pen-gun-project-t7858.html
thanks to Surfguy21 for this info
Step 1: Parts
For this project you will need a bic pen and another piece of tubing (I got mine from a mechanical pencil) that fits inside the front peice of the bic pen if you remove the ink cartrige. You will also need a Zebra mini mechanical pencil (got from staples) or an eraser that fits inside a bic pen and you can drill a hole through. You need a schrader valve (the ones used on bike tires), and a airsoft bb.
Step 2: Tools
All you need for this is a knife and some epoxy.
Step 3: Get the schrader valve
The best way to do this is to get an old bike innertube and cut the schrader valve out, then sand off about 3/8 of an inch of the rubber off exposing the brass.
Step 4: Taking apart the pen
This is really simple just disassemble the Bic pen and keep all the parts.
Step 5: Prepare the eraser
All you need the Zebra pencil for is its eraser and spring. The spring is pretty self explanatory, just bust apart the pencil and take the spring out. The eraser will serve as a seal it will go on the end of the larger tube (not the ink cartridge) and be sealed when the airsoft BB touches it. In the drawings pink is the eraser.
Step 6: Prepare the end cap
This step is a lot like the eraser step just cut off the end cap of the pen so you end up with a plastic tube.This is the black part in the middle of the drawing.