How to shoot RayCast in center of screen?

I need some scripting help

My Code

 #pragma strict
 var damage : float = 1;
 
 var bulletsinclip = 30;
 var bulletsperclip = 30;
 var clips = 3;
 
 private var nextFireTime = 0.0;
 var fireRate = .02;
 
 
 function Update () {
 if (Input.GetKeyDown (KeyCode.R)){
 Reload();
 }
 if (Mathf.Abs(Input.GetAxis("Vertical")) > 0.1)
 animation.CrossFade("Move");
 else
 animation.CrossFade("Idle");
 
 if (Input.GetKeyDown (KeyCode.G)){
 animation.Play("select");
 }
 
 if (Input.GetKeyDown (KeyCode.H)){
 animation.Play("Put Away");
 }
 
 if(Input.GetMouseButton(0)){
 if (Time.time - fireRate > nextFireTime)
 nextFireTime = Time.time - Time.deltaTime;
 while( nextFireTime < Time.time && bulletsinclip != 0) {
 FireOneShot();
 nextFireTime += fireRate;
 }
 }
 }
 
 function Reload(){
 animation.Play("Reload", PlayMode.StopAll);
 bulletsinclip = bulletsperclip;
 clips --;
 }
 
 function FireOneShot(){
 animation.Play("Auto");
 bulletsinclip -= 1;
 
 var direction = transform.TransformDirection(Vector3.forward);
 var hit : RaycastHit;
 var localOffset = GameObject.Find("GunTip").transform.position;
 if (Physics.Raycast (localOffset, direction, hit, 300)) {
 Debug.DrawLine (localOffset, hit.point, Color.cyan);
 // - send damage to object we hit - \\
 hit.collider.SendMessageUpwards("ApplyDamage", damage, SendMessageOptions.DontRequireReceiver);
 }
 }
 
 function OnGUI () {
         GUI.Label (Rect (10, 10, 100, 20), "Ammo: " +bulletsinclip);
         GUI.Label (Rect (10, 30, 100, 20), "Bullets Left: " +clips * 30);
 }

I understand that the "bullets" (raycast) shoots from the guntip but how do i make it go to the center of the screen?