there are only two turrets, but they are invisible and tough to kill so it can seem like more! The first turret spawns in the middle of the chamber when you cross the threshold, and the second spawns by the door later when you reach the far end of the room.
This method works for me:
- shoot the door open and destroy any boxes without entering the room.
- make a save (it can take several attempts to get this right!)
- quickly enter just inside the doorway, then immediately back out again and crouch down behind the wall to the left of the door. If you did it right, the far turret will spawn and you just have enough time to get out of its sight before it kills you.
- from your hidden position, throw F1 or other powerful grenades at the right wall of the chamber, so they bounce back into the middle. Two or three should kill the turret - watch for a bigger thanusual explosion.
- Make another save just in case, then enter the room. If you were successful (i.e., if you aren't now dead) head down the side of the room.
- The second turret by the door should spawn as you get near the far end, so quickly get behind the end pillar on the right. Without letting the turret see you, throw more grenades in the direction of the doorway. Again, two or three should kill the turret.
Alternatively, change to "God mode", walk up to them and drop grenades on top of them.