In the aftermath of WW2, the Norwegian Army had a large assortment of open bolt guns. MP40s, MP35s, Thompsons and Soumi KP31to mention a few... A lot of people experienced the runaway gun phenomenon when loading weak pistol ammo into these guns, who were intended to be used with "MP"-ammo. A dude I know with a collectors permit and an open bolt UZI demonstrated this with his own home made 9mm reloads.
Fun fact; the MG34 will chamber and fire 6,5x55 reliably, but not accurately
