Step 1: Materials
A tube at least three inches long
Small weight (optional)
Spring a little longer than tube
String or fishing line
Rod the same width as the tube's hole
Step 2: Getting started
The video's pretty bad, sorry about that. You shove the rod into the tube, and make sure the notch lines up with the hole. You will then put the thin rod into the hoe to lock the spring. Dont put the thin rod in too far. The thin rod can be replace by anything, preferably a hook. You can then attach a fishing line to the hook. Gently place (dont stick hard) duct tape on the opening after putting some bb's.
Now you are ready to launch. This is reusable if you could not figure that out on you own. When you throw this, hold on to the other end of the line. Once its far enough, it will lanch all of the bbs as the hook is yanked out. This is convenient since you dont have to buy an expensive reusable. Put some spin on it so the bb's dont all go in one direction. If the key doesn't pull out, add a weight and make sure it is not too far into the hole. I borrowed this concept from a land mine you tube video. I also made a multi bb launcher with a big spring and attached it to the side of my gun.