Looks like something that could be made at just about any machine shop.
The problem would be getting enough ammo to ‘Spray and Pray’.
A full auto has its uses, but for most work a semi-auto is a lot more accurate and certainly a lot more economical re ammo.
Exactly & that is what scares the political class silly & with 3D printing makes it even simpler for those who don’t have heavy duty machine tools in the basement. The STEN gun is a simple weapon but with 3D printing you can make parts for bigger & far more effective weapons.