The Hampton MPL 9mm SMG (The Walther MPL) has a 30 round magazine capacity, is chambered in 9x19mm and has the ability to mount a sound suppressor. It can use FMJ, Dum-Dum, and incendiary ammunition.
A few factions in the game use the Hampton MPL 9mm SMG as their standard SMG, including UNITY's commandos and Magnus Armstrong's H.A.R.M. paratroopers.
A vicious little 9 mm submachinegun. Elegantly simple and hardy.
Walther MP on Wikipedia