Step 1: Lets GO!
Ok, now we need a click pen. The one pictured works best (and they are mostly free from car delerships) because it comes apart nicely.
We also need a lighter, or like i did the first time you can use a stove if you are really carefull. A projectile can be found later, i use erasers from cheap pencils.
DISCLAIMER: this project can possibly injure somebody. I am not responsible for any injuries, damages or deaths related to the fabrication or usage of this product. Allways use common saftey sense and proper saftey equipment while fabricating or using this product. It can shoot over 100ft and still sting a little.
This was origionally posted my me at (http://sirscamit.tripod.com/id12.html)
Step 2: Pen to Barrel
Now take the plastic straw from the air duster and stick it into where the ink tube was not so long ago. It probably wont fit too snugly so this is where the lighter (or stovetop) comes in. CAREFULLY melt the tip untill it's barely soft and roll it on the desktop to shrink the diamater of the tip to fit the straw fairly snugly.
It should be fairly difficult to pull it off of the straw because it will be holding pressure later. Now we need to finish up. If my vague discriptions haven't helped, the pictures should help.