Dude its called paint and zippy ties.

Nice cannon. Wish I could come up with first ideas for cannons though Oh well once my mini shot guns finished I'll see about making a hybrid Killa for his double barrel gets my vote. Lets see something good Urban

Using a fan in the chamber mixes the air and fuel about resulting in a beter air fuel ratio.

Have you got any construction pics? It would be cool to look at before and after photos

I suggest a simply putting a box on top of a tube that feeds the BB's into a flowing airstream. That and put all the barrels close together like touching side to side. Just a suggestion