Make bullet launch at center of screen

I've tried searching around for a code to fire a bullet to center of screen I know it has to do with ray cast but I don't know how to implement it in my code Thanks

 var bullet : Rigidbody;
 var power : float = 1500;
 var damage : float = 100;
 var reloadtime : float = 1.5;
 var magcount : int = 10;
 var magbulletcount : int = 9;
 var bulletcount : int = 0;
 var rtext : boolean = false;
 var bulletTex : GameObject[];
 var firing : boolean = false;
 var clip : AudioClip;
  
 private var reloadTimer: float = 0.0; // internal reload timer 
 function Start () {
   bulletcount = magbulletcount;  
 }
 Screen.showCursor = false;
 function Update(){
 
     if (reloadTimer > 0){ // if reloadTimer active...
     rtext = true;
         reloadTimer -= Time.deltaTime; // decrement it
         if (reloadTimer <= 0){ // if reloadTime ended...
         rtext = false;
           bulletcount = magbulletcount; // load a full clip...
           magcount--; // and decrement clip count
         }
       } 
       else // only shoot when reloadTimer not active
       if (Input.GetButtonDown("Fire1")&& bulletcount > 0){
       var instance : Rigidbody = Instantiate(bullet, transform.position, transform.rotation);
       var fwd : Vector3 = transform.TransformDirection(Vector3.forward);
       instance.AddForce(fwd * power);
       var hit : RaycastHit;
         firing = true;
         bulletcount --;
         if(Input.GetButtonDown ("Fire1") && Physics.Raycast(transform.position, fwd, hit, 10)&& bulletcount > 0){
 Instantiate(bulletTex[Random.Range(0,3)], hit.point, Quaternion.FromToRotation(Vector3.up, hit.normal)); 
 }
         if (bulletcount <= 0 && magcount > 0){
           // if run out of ammo but still have clips...
           reloadTimer = reloadtime; // activate reloadTimer
           // you can play reload sound or animation here
         }
       }
     if (Input.GetKeyUp(KeyCode.R) && magcount > 0 && bulletcount < magbulletcount){
     reloadTimer = reloadtime;
     }
     if(firing && !audio.isPlaying){
 audio.PlayOneShot(clip);
 }
 if(!Input.GetButtonDown("Fire1")){
 firing = false;
 }
 }
 
 var originalWidth = 1024.0;  // define here the original resolution
 var originalHeight = 768.0; // you used to create the GUI contents 
 private var scale: Vector3;
 
 function OnGUI(){
 scale.x = Screen.width/originalWidth; // calculate hor scale
 scale.y = Screen.height/originalHeight; // calculate vert scale
 scale.z = 1;
 var svMat = GUI.matrix; // save current matrix
 // substitute matrix - only scale is altered from standard
 GUI.matrix = Matrix4x4.TRS(Vector3.zero, Quaternion.identity, scale);
 // draw your GUI controls here:
 GUI.contentColor = Color.yellow;
 GUI.Box(Rect(10,10,200,55), "Lawrence Mercieca's game test \n \n(PRE ALPHA TESTING PHASE)");
 GUI.Button(Rect(20, 680, 50, 30),bulletcount+" / "+magcount);
 if (rtext){
 GUI.Button(Rect(20, 720, 100, 30), "RELOADING");
 //...
 // restore matrix before returning
 GUI.matrix = svMat; // restore matrix
 }
 }