I had a chance to shoot a full auto one with it's obtrusive 50 round magazine a couple years ago at a local museum. A friend was shooting a silenced UZI next to me, and wanted to know if I wanted to try the UZI. Not a chance.....I far preferred firing that piece of history. That 50 round magazine just seemed to run on forever.
I have a dewat Lanchester downstairs somewhere. Too heavy in my mind to qualify as a sub machine gun.....borders on a LMG.