rotating a tank turret while the tank is rotating

Hi, im new to unity and i need help.

I want to rotate a turret of a hetzer (just google it, its a tank) The turret is fixed at the front of the tank and can only move there (just google hetzer to see what i mean).

when the tank is not mooving, its working fine, but when i rotate the tank at the same time as i rotate the turret, then the turret rotates out the the boundaries, here is the script:

 public var gunPrefab:Transform;
 private var gun:Transform;
 
 
 
 
 function Start () {
 gun = Instantiate(gunPrefab,transform.position,transform.rotation);
 gun.parent = transform;
 
 }
 
 
 
 function Update () {
 
 var temp : Vector3;
 temp.x = Input.GetAxis("Mouse Y") * (-1) ;
 temp.y = Input.GetAxis("Mouse X") ;
 temp.z = transform.rotation.z;
 
 
 
   
 
 if((temp.x > 0 && gun.rotation.x > 0.1) || (temp.x < 0 && gun.rotation.x < (-0.1)))
 {
     temp.x = 0;
 }
 if((temp.y > 0 && gun.rotation.y  > 0.15) || (temp.y < 0 && gun.rotation.y  < (-0.15)))
 {
     temp.y = 0;
 }
 
 gun.transform.Rotate(temp);

 }