Thanks to Kei Kimura for sending this our way. His friend made a 1:1 scale replica of a Barret M82A1 out of cardboard. In Japan this art form is called “Papercraft”. Usually papercraft are made of sheets of paper cut, folded and glued into shapes. This is made of cardboard understandably because of the size and weight. It takes a bit of set up but the action works and ejects the casing out. The audience are more than ecstatic when they see it work.
Here is a link to a page about the build for this project.