WARNING- This can really hurt someone. Do not aim at eyes or any other person/animal(s). This was made for recreation and the fun of inventing.
Step 1: Materials:
1. A tube 5mm in diameter and a little less that 2 inches long.
2. 4 rubber bands.
3. Optional- a tube 1-2mm in diameter and 2 cm in length as viewfinder.
Step 2: The Tube and rubber band
Length- less than 2 in.
Take the tube and take 2 rubber bands. Fold one of the rubber bands over so that it is a U. Place each end of the U on either side of the end of the tube. Than take the other rubber band and keep wraping it around the tube with the rubber band U on it until taught. test by pulling on the U shaped rubberband.