Those junk machine pistols fire from an open bolt I think.......
Those M10's are actually very rugged. They are also modular and parts/barrels, etc. are easy to replace. There's nothing wrong with an open bolt sub-gun, both UZI and Thompsons are made with open bolts. In fact, open bolt design has some distinct advantages in sub-gun design. It keeps the barrel cooler and doesn't let a locked round "cook-off" in the chamber. They are better designed to be short range bullet-hoses.