pistol recoil rotation

hey, i been trying to make a gun recoil for my pistol and i have a script attached to my gun model.the script works fine somehow... it rotates on x axis about 15 degree. but as i shoot more and more, the gun rotates less and less until it's rotation becomes absolute zero. i created a GIF to show the issue. http://s6.uplod.ir:182/d/2k22yze74hvhuf6tpwoij6jhvjz43kmq7soreocqgk3u7tb2ezzyi6knvdjshyn7mibngw7g/GIF_20180627_162008.gif and here is the script : public class recoiltesti : MonoBehaviour { Vector3 recoilSmoothDampVelocity; public float recoliEnergy;

     public float FireRate;
     private float NextTimeToFire = 0f;
     public float recoilAngelSmoothDampVelocity;
     public Quaternion originalRotationValue; // declare this as a Quaternion
     public float rotationResetSpeed = 0.1f;
     float recoilAngle;
     void Start () {
         originalRotationValue = transform.rotation;
     }
 
     // Update is called once per frame
     void LateUpdate() {
         // animate recoil
         recoilAngle = Mathf.SmoothDamp(recoilAngle ,0 ,ref recoilAngelSmoothDampVelocity,0.1f);
 
         transform.localEulerAngles = transform.localEulerAngles + -Vector3.forward *recoilAngle;
 
 
         if (Input.GetButtonDown("Fire1") && Time.time >= NextTimeToFire) {
             NextTimeToFire = Time.time + 1f / FireRate;
 
 
             shoot ();
 
         }
         else{
             resetRot ();
 
         }}
 
 
     public void shoot ()
     {
         
         recoilAngle += 15;
         recoilAngle = Mathf.Clamp (recoilAngle, 0, 25);
 
     }
 
     public void resetRot ()
     {
         transform.rotation = Quaternion.Lerp (transform.rotation, originalRotationValue, Time.time * rotationResetSpeed);
 
     }
 }