To make a BB gun with a pen, remove the ink tube and the ends from a ballpoint pen. Remove the lead from a mechanical pencil, and put the hollow tube inside the pen. Cut a notch in the eraser, and wrap the pen with rubber bands.
- Hollow out a pen
Start with a ballpoint pen. Remove the ink tube from inside the pen. Cut off the ends of the pen with a pair of scissors, knife or wire cutter. This hollow tube forms the outside of the BB gun.
- Hollow out a mechanical pencil
Cut the writing end off of a mechanical pencil. Remove all the pieces of lead from the pencil. The tube should be narrow enough to fit within the pen tube. Cut down the pencil tube to be shorter than the pen tube. Put the pencil tube into the pen tube.
- Cut a notch in the eraser
Cut a notch through the center of the eraser on the end of the pencil. Put a rubber band into the notch.
- Wrap the pen with rubber bands
Pull the rubber band on the eraser toward the other end of the pen tube. Wrap one or two other rubber bands around the pen tube to secure the first rubber band in place. Put a BB in the front of the pen tube. To fire the pen gun, pull back on the eraser end of the pencil and release it. This gun is dangerous, so do not fire at living things or look down the barrel while a BB is in it.