I think that everything is all right...why it doesnt work correctly?

 // The speed the bullet moves 
 
  var Speed : float = 0.4; 
    
    // The number of seconds before the bullet is automatically destroyed 
    var SecondsUntilDestroy : float = 10; 
    
    private var startTime : float; 
    
    function Start () {
        startTime = Time.time; 
    } 
    
    function FixedUpdate () {
        // Move forward 
        this.gameObject.transform.position += Speed * this.gameObject.transform.forward;
        
        // If the Bullet has existed as long as SecondsUntilDestroy, destroy it 
        if (Time.time - startTime >= SecondsUntilDestroy) {
            Destroy(this.gameObject);
        } 
    }
         
    function OnCollisionEnter(tc : Collision) {
        
        // Remove the Bullet from the world 
        Destroy(this.gameObject); 
    }