This guns entity name is “weapon_teslagun” Its unique so obviously it’s a very powerful gun.
It has 100 units of ammo without any magazines and clips, sadly it’s not possible to recharge it, all you can do is get another tesla gun. It is similar to egon or gluon gun in Half-life.
It’s down under dams water, not in the reservoir its in the drain side, at the very end.
You are in a mansion. There is a elevator to underground labs. It’s in second floor of underground labs entrance.
At the second floor of living quarters, throw a grenade into this rooms window. If you have no grenade, then u can get some from one room that is one floor below.
Under the waterfall, however be careful because there are two ichthyosaurs in the water.
In the cage where you’re gonna get trapped ,although you cant use it because your weapons are gonna get stripped after this scene.
After climbing the ceiling go left, you should find it freely laying down.