Collider question

Hello, i'm making a collision-damage system This is my script:

 function OnCollisionEnter(collision : Collision)
 {
   health = health - damageConstants*collision.impactForceSum.magnitude;
    if (health <= 0){
    DestroyObject();
    }
 }

---And there is my bullet script:

 var BulletSpeed = 7000;
 var Smoke : GameObject;
 
 function Start () 
 {
     rigidbody.AddForce(transform.forward * BulletSpeed);
 }
 
 function OnCollisionEnter (collision : Collision)
 {
     Instantiate(Smoke , transform.position, transform.rotation);
     Destroy (gameObject);
 }

But i found there is no difference between (7000 force - 1 mass in rigidbody) vs (700000 force - 100 mass in rigidbody) damage cause, it's the same damage, could someone help me out, I want to make more types of bullet. Thanks all.