The 9x19VSN is described in the game as:
This SMG is the AK47’s kid brother.
It’s found in northern Inca Camina province, inside Inca Camina base. The weapons case is on the roof of a building at the eastern end of the base, near the main entrance.
The quick approach would be by parachute, landing next to the weapons case on the roof, but this is risky. The base has a jammer, which makes scouting it difficult unless you’ve upgraded your drones range and zoom, but I suggest the elevated approach to the base from the north.
Start by taking out the snipers in the guard towers so you don’t have to worry about them later. You can get in near the generator and turn that off on your way to the weapons case. Enemies are sparse here and easy to take out. You have to enter the building and go up the stairs all the way to the top to get to the weapons case.
If you like to use an SMG, this one accepts pretty much all the attachments you can throw at it, and is only bested in handling by the MP7 and MPX. However, it’s not one of the quieter SMGs.
It has a 20 round standard magazine, the 30 round extended magazine can be found in Villa Verde.