The creativity of some people really impresses me.  While I’m not sure of the legality of this (in the US, would this qualify as an SBR? https://www.atf.gov/firearms/qa/does-gca-prohibit-anyone-making-handgun-shotgun-or-rifle), it is pretty decent craftsmanship.  The poster (Youtube: pyroneph) even goes so far as to shape and oil the stock.  I could see staging a little war re-enactment with miniatures on a table top (or other such geeky imagining).  Just don’t put your eye out… 🙂

I originally saw it posted on Imgur, but it looks like it was actually filmed a few years ago (below is the Youtube posting):

He also has some other miniature gun creation videos (and one for a pocket katana, if that is your thing).  It just goes to show, a little bit of ingenuity goes a long way, and building simple firearms is really not all that difficult…