A little hairy to use and very inaccurate, because it fires from an open bolt, but certainly an easily built weapon. Magazine feed is a real problem (it sticks out sideways, people tend to grab it, and the lips of the magazine deform — plus it shows around cover) and it jams pretty easily as well. My dad served with the Brits and they hated the thing - called it the “stench gun” or the “plumber’s helper”.
An Aussie squadie came up with a vastly improved version, the eponymous Owen SMG.
Diggers loved it in Burma and Malaya, IIRC