Trying to rotate weapon

i am trying to rotate the weapon until it gets to a certain rotation(Stop the rotation).

this is the code

 function Update () {
     if(Input.GetKey(KeyCode.A)){
         transform.Rotate(Vector3.right * Time.deltaTime * 10);
     }
     if(transform.eulerAngles.x >= 5.1){
         transform.eulerAngles.x = 5.1;
     }
 }

I am walking left and its simply rotates. when the x gets to 5.1 i want it to stop even though i am still walking left.