increase linecast length

Im creating a 2d game where a player points at objects to shoot at them but i want to use linecast instead of bullets. im trying to increase the length of the raycast so the player only hast to aim in the direction but when i multiply the end position it loses accuracy.

heres my code:

 #pragma strict
 var AttachedCamera:Camera;
 function Start () {
     
 }
 
 function Update () 
 {
 
     var MousePosition = this.AttachedCamera.ScreenToWorldPoint(Vector3(Input.mousePosition.x,Input.mousePosition.y,Mathf.Abs(this.transform.position.z + this.AttachedCamera.transform.position.z)));
     var hit:RaycastHit;
     if (Physics.Linecast (this.transform.localPosition, MousePosition - (), hit)) {
         if(Input.GetMouseButton(0))
         {
             Debug.DrawLine(transform.position, hit.point, Color.red,10);
             Destroy(hit.collider.gameObject);
         }
         Debug.DrawLine(transform.position, hit.point, Color.blue);
     }else
     {
          Debug.DrawLine(transform.position,MousePosition, Color.green);
          //Debug.DrawLine(transform.position, MousePosition + MousePosition, Color.cyan);
     }
    
     
     
 }

How can i extend the length without losing accuracy? thanks in advance