Bukullu69 of YouTube found a way to make a bb gun at home, and he is instructing us how to do so. First, you must get a ballpoint pen, and remove the ink tube, so you get a hallow cylinder. Then take a mechanical pencil, and remove the lead tube, leaving you with a hallow cylinder with an eraser on it. Now cut the mechanical pencil tube to a length slightly shorter than the ballpoint pen tube, cutting off the end where the lead usually comes out. Insert the mechanical pencil tube into the pen tube, where it should be stopped by the eraser. Now cut a notch into the eraser, and put a rubber band into the notch. Pull the rubber band down most of the length of the pen. Hold this in place with another rubber band securing the first rubber band to the body of the pen. You may wish to secure with more than one rubber band. From here, you can insert a bb into the pen tube, pull back on the mechanical pencil's eraser housing, and release to launch the bb.