Help! Can't destroy my bullet object because is a rigidbody

 // Did the time exceed the reload time?
 if (Time.time > reloadTime + lastShot && ammoCount > 0) {
     // create a new projectile, use the same position and rotation as the Launcher.

     var bullet : Rigidbody = Instantiate (bulletPrefabs, spawnBullet.transform.position, Quaternion.LookRotation(inputRotation));

     //Destroy(bullet, 3.0);

     bullet.velocity = tempVector * initialSpeed;
     //bullet.rigidbody.AddForce(transform.right * 2000, ForceMode.Acceleration);
     // Ignore collisions between the missile and the character controller
     Physics.IgnoreCollision(bullet.collider, transform.root.collider);



     lastShot = Time.time;
     ammoCount--;

 }