Knex Gun Prototype

Prototype of a rubber band powered knex gun. I am looking for modifications, improvements, and ideas. At its current state the gun will fire a single shot. I am trying to include: a trigger, ammo storage, automatic loader, and better bullet design/idea. The gun is relatively simple to make and does not require a lot of pieces.

Step 1: Build Support Base

Build a base out of:
8 Yellow Connectors
2 Blue Rods
2 White Rods
10 Green Rods

Pretty Simple, see picture

Step 2: Build Firing Rod

Build the firing rod with the following pieces:
1 Yellow Connector
1 Orange Connector
1 Green Rod
1 Grey Rod
1 Small/Medium Rubber Band

Very simple, see picture

Step 3: Build Barrel / Firing Rod Centerer

This centers the firing rod and holds the bullet. You need:
4 White Connectors
4 Red Rods
2 Grey Rods
1 Blue Rod

The Red and Grey Rods are for added support; the blue rod holds the rubber band

Step 4: Attach Pieces to Make Gun

Attach the pieces as shown in the picture.
The firing rod slides through all four white connectors.
The bullet is undeveloped. I have been using a white rod with a red connector; this definitely needs improvement.

First instructable, please let me know any ideas to making this gun better.