https://en.wikipedia.org/wiki/Philip_Luty#Firearms_design

> one particular design, outlined in his book Expedient Homemade Firearms, is the best known. This design makes extensive use of easily procured materials such as folded sheet metal, bar stock, washers, and hex screws. It is a simple blowback-operated sub-machine gun and entirely made from craft-produced components, including the magazine and pistol grip. The major drawback of such designs is the lack of rifling in the barrel, which results in poor accuracy and limited range

This book was openly sold on Amazon 10 years ago. I still have one on my shelf.

See it in action: https://www.youtube.com/watch?v=3YE9J7qcj0c