It is based on the real life MP7.
SAS: Zombie Assault 2
The MP7 is one of the premium weapons, and possibly the best value for money premium weapon there is. It combines infinite penetration (hit through all zombies regardless of number) with a very high move speed and quick reload time, making it effortless to walk backwards faster than you were attacked and hit as many zombies as you could (easily 50 at once) which makes for a very high damage into groups.
SAS: Zombie Assault 3
It is unlocked at Rank 25, and is best for taking out basic Zombies. It costs $30,000, and ammunition for this gun costs $25 for 250 rounds. It seems to be the upgraded version of the MP5. This gun is great in all aspects except for damage output. If you find you can still use your Vector right now, this might be worth a look at. With almost the damage of a Vector and the fire rate of the Skorpion, it is quite good. This is the first SMG with pierce, and it excels in that. Hitting 3 zombies each shot, crowd control is the primary feature of this gun. However, with a cost of $30,000, the choice is yours on whether you want to fork out the cash for the MP7.
MP7 deals 105 damage (131 for upgraded damage).