This is based off of a video that I saw on Youtube owned by ZEUKI1. I added a couple things but this piece was made by me on MS Paint. It's a basic cannon so anyone can build it.

But this is the cannon idea that I will probably use in my airsoft tank that I am planning on building...I will upload schematics later.

When this cannon recoils, it ejects the spent "shell" and springs back to it's original position, waiting to be fed another round.