void Main(){ 

    //create a list to gather the turrets into

    List<IMyTerminalBlock> turrets = new List<IMyTerminalBlock>();



    //populate that list with every block in the ship which is a turret

    GridTerminalSystem.GetBlocksOfType<IMyLargeTurretBase>(turrets);



    //loop through each turret in the list...

    for(int i = 0; i < turrets.Count; i++){

        //...assign each one in turn to this variable...

        IMyTerminalBlock turret = turrets[i];

        //...and apply its 'toggle off' action

        turret.GetActionWithName("OnOff_Off").Apply(turret); 

    } 

}