smoother rotation

hi, I am using mathf.clamp to limit the rotatin of a barrel in unity, but its jerky. Here is the code:

 #pragma strict
 
 var current_rotation : int = 0;
 var Extra_Rotation : float = 1.05;
 
 function Start () {
 
 }
 
 function Update () {
     
 }
 function FixedUpdate () {
     current_rotation += -Input.GetAxis("Vertical") * Extra_Rotation;
     current_rotation = Mathf.Clamp(current_rotation, -20, 15);
     
     transform.localEulerAngles = new Vector3(transform.localEulerAngles.x, current_rotation, transform.localEulerAngles.z);
 }

if you know anything I would appreciate it.