How can I add force to a raycast bullet?

I'm working in a FPS. I've got a GunScript that instantiates a basic "bullet" when mouse button is pressed. The bullet uses raycast. What i wanted to do is to add force to the rigidbodies that the bullet hits, so it could shoot to objects (boxes, enemies, etc) and make them move by the force of the impact.

But for any reason it's not working! I would be glad if you lend me a hand on this, guys..

What I tried is defining:

var bulletDirection = transform.TransformDirection(Vector3.forward);

and then use:

              hit.rigidbody.AddForceAtPosition (bulletDirection * bulletForce, hit.point);

this is the script:

 var range : float = 50; 
 var bulletHole : GameObject; 
 var blood : GameObject; 
 var floatHeight : float = 0.001; 
 
 var damage : float = 1; 
 var bulletForce : float = 10000;  
 
 function Update () 
 {
     var hit : RaycastHit;
                     //    var bulletDirection = transform.TransformDirection(Vector3.forward);
     if (Physics.Raycast(transform.position, transform.forward, hit, range))
     {
         if (bulletHole && hit.transform.tag == "bulletHoleReceiver") 
             Instantiate(bulletHole, hit.point + (hit.normal * floatHeight), Quaternion.LookRotation(hit.normal)); 
 
         if (blood && hit.transform.tag == "Enemy") 
             {
                      // hit.rigidbody.AddForceAtPosition (bulletDirection * bulletForce, hit.point);
             Instantiate(blood, hit.transform.position, hit.transform.rotation);
             hit.transform.GetComponent(EnemyScript).enemyHealth -= damage; 
             }
     }
     Destroy(gameObject);
 }

Sorry for my poor english.