Here is a very simple yet powerful K'nex projectile launcher with a ammo rack. It is very easy to make and uses only the very basic K'nex pieces. If you like this please don't forget to vote!!
Step 1: Build the Base
The base is very simple to build. Just attach 8 Yellow rods to 2 white connectors like the photos show.
Step 2: Add the Rubber-band
Attach the rubber-band to the base. This is a little tricky to do. If you don't like how i did it, just put it on your way, it does not make much of a difference.
Step 3: Build and Attach the Ammo Rack
The ammo rack is optional, it is much nicer if you have a ammo rack because you can hold up to 5 grey rods. (The ammo)
Step 4: Add the Ammo to the Ammo Rack
The last step and the easiest step is the last step, just add the ammo to the ammo rack.
Congratulations!! You are done with your K'nex Projectile launcher!!