5. Magpul FMG-9 The Magpul FMG-9 is a prototype for a new generation of folding submachine guns, designed by Magpul Industries in 2008. It is made out of a light-weight polymer material rather than metal, making it very light and easy to carry. It is still a prototype and may or may not be made in large numbers for law enforcement agencies. The prototype uses a semi-automatic firing mechanism from a 9mm Glock 17 pistol.