Issue with Bullet Movement shooting

Hi , After Hours Coding Finally i got the problem . The Bullet Not Moving in z Direction relative to Camera Z direction . i dont know what is supposed to be wrong with my code . I guess i did right way when make that script . Here is the code : ![alt text you can see my Bullet not Moving along z direction relative of Camera, but aside slightly . I dont know how to Fix it

     public class MenembakUjiCoba : MonoBehaviour {
        
         public float fireRate = 0.5f ;
         public float bulletSpeed = 100.0f;
         public WeaponType weaponType ;
         //public AudioSource source ;
         public float nextFire = 0.0f;
         public Vector3 posisiPeluru ;
         public Ray ray ;
         public RaycastHit hit ;
         // Use this for initialization
         void Start ()
         {
         weaponType = WeaponType.Automatic;
        
         }
        
         // Update is called once per frame
         void Update ()
         {
             if(Input.GetMouseButton(0))
             {
                 if(weapon == WeaponType.Automatic && nextFire < Time.time)
                 {
                     GameObject bullet = Instantiate((GameObject) Resources.Load("Bullet/bullet",typeof(GameObject)),PlaceInstantiate(),transform.rotation) as GameObject;
                     bullet.rigidbody.AddForce(transform.forward * bulletSpeed);
                     Debug.Log(Vector3.Dot(transform.forward,bullet.transform.TransformDirection(transform.forward)));
                     bullet.rigidbody.useGravity= false;
                     ray =new Ray(transform.forward,bullet.transform.forward);
                     if(pel.collider.Raycast(ray,out hit,0.0f))
                     {
                         if(hit.collider.CompareTag("Enemy"))
                         {
                             Debug.Log("Hit Musuh");
                             Destroy(pel);
                         }
                     }
                     nextFire = Time.time + fireRate;
                 }
             }
        
         }
        
         public enum WeaponType
         {
             Automatic=0,
             Manual=1
         }
        
         public Vector3 PlaceInstantiate()
         {
             return  Camera.main.ScreenToWorldPoint(new Vector3(Screen.width/2,Screen.height/2,Camera.main.nearClipPlane ));
         }
     }