SpudFiles

The front sight has this animated guy holding a build and i like how it looks. The larger tube with the smaller one inside it looks cool but ive never seen anything like it.

Here's a link to the cannon in the image: http://www.advancedspuds.com/pneumatic.htm. You should be able to suss out how to build it by looking closely at that page.

What does the cut in the front do? its like a little slot cut into the outter coupler

Nothing, it's not on the original. It looks like whoever created the logo mistook a couple of primer stains as a cut-out.