UPDATED: New gun design and instructable steps, 08 april
Minor Update, 12 april: Ive redesigned the firing levers to stop misfires. The changes are very small but important. The very last section has a photo of the modifications.
I agree with the comments saying the gun was too bulky. Ive remade it into a much more compact and powerful design. The first few steps are the same, but theres more ones been added to show the new design. Ive also got a video of the gun firing.
I will begin this with the obligigatory "my first instructable etc....". With that out the way, onto the gun. (by the way, I know my username is spelled wrong).
This gun holds 8 shots, and will fire them as fast as you can pull the trigger. It can fire several types of connector. Using two bands per shot, it fires about 30-40 feet, though It has the potential for much more.
It does not require many "exotic" parts, however you do need quite alot of bands. I needed 19: 16 for the barrel, 1 for the barrel spinner, and 2 for the trigger return mechanism.
The basic idea is that the barrel holds the 8 shots in a ring. The barrel is tensioned by a band which makes it rotate betweeen each shot. When you pull the trigger, a level flicks one shot out of the barrel, and at the same time moves a ratchet which advances the barrel one "click", lining up the next shot. This mechanism can work very quickly- I can fire off all 8 shots in under two seconds.
Note: If you fire this at hard surfaces, it tends to break parts off the ammo. Also, the shots rebound very easily and can hurt if they hit you.