This is a little gun I came up with because i was bored. It gets a pretty good range depending on the band and is very simple.

Thing you need
~A few knex pieces(haven't counted)
~1-2 small rubberbands

Step 1: Barrel and Firing Pin Assembly

This doesn't need a real description the pictures should explain it.

Step 2: Handle Assembly

Step 3: Rubberbanding

Depending on the bands you use this will very quite a bit. But here is the method i use.Ignore the extra peices laying around. When the firing pin is inserted move the rubberbands to the left of the trigger. This will make it lock when the pin is pulled back.

Step 4: Loading and Firing

Pull back the firing pin. THe trigger should automatically lock. Then load your ammo into the barrel. The small black rods, the little bigger grey rods, and ball bearings all work great. Move the trigger to the left to fire. Constructive Crtisism welcome, but be nice...this is my first instructable.