These were made by Guide Lamp and Marlin. They were originally .45 and they made some in 9mm for yuk and chuckles...they had sights. They were FA but with a slow rate of about 300 RPM they could be tapped single easily.
M3 submachine gun - Wikipedia, the free encyclopedia
I had one for a bit, the springs had been eaten by rust. I used the small springs out of a buttstock of an FN I think it was. The gun ran so fast it would have ten empties in the air at once...I had to have springs made and then it was much closer to original speed.