FPS rigidbody bullets not moving to center of screen

I am making an fps. How do i get the bullets to shoot at the center without ads? BTW I am using rigidbody bullets. The bullets come from the gun, which is not slanted, and also, the bullets are straight.

My code:

using System.Collections; using System.Collections.Generic; using UnityEngine; using TMPro;

public class fireGun : MonoBehaviour { public GameObject gun; public GameObject bullet; public Transform gunStart; public float fireTime; public int bulletCount; public int magLeft; public bool ready; public Animator gunAnim; public AudioSource SFX; public AudioClip gunShot; public bulletProperties bProp; public LineRenderer lRend; public GameObject gunSmoke; public bool reloading; public TMP_Text shotText; // Start is called before the first frame update void Start() { gun = this.gameObject; fireTime = 0f; gunAnim = gun.GetComponent(); SFX = GameObject.Find("Sounds").GetComponent(); bProp = bullet.GetComponent(); lRend = gun.GetComponent(); magLeft = bProp.magSize; shotText = GameObject.Find("bulletsLeft").GetComponent(); reloading = false; }

 // Update is called once per frame
 void Update()
 {
     shotText.SetText(magLeft + "/" + bProp.magSize);
     lRend.SetPosition(0, gunStart.position);
     lRend.SetPosition(1, gunStart.forward * 1000f);
     if (fireTime <= 0f)
     {
         ready = true;
     } else
     {
         ready = false;
         fireTime -= Time.deltaTime;
     }
     if(magLeft <= 0 && !reloading)
     {
         reloading = true;
         gunAnim.SetTrigger("Reload");
         Invoke("Reload", bProp.reloadTime);
     }
     if (ready == true && Input.GetMouseButton(0) && !reloading)
     {
         Shoot();
         if(bProp.burst == true)
         {
             Invoke("Shoot", 0.15f);
             Invoke("Shoot", 0.3f);
         }
     }
 }

 void Shoot()
 {
     GameObject gSmoke = Instantiate(gunSmoke, gunStart.position, new Quaternion(0, 0, 180, 0));
     Destroy(gSmoke, 2f);
     magLeft--;
     for (int i = 0; i < bulletCount; i++)
     {
         GameObject bulletInstance = Instantiate(bullet, gunStart.position, gunStart.rotation);
         Rigidbody bRb = bulletInstance.GetComponent<Rigidbody>();
         gunAnim.SetTrigger("Shoot");
         SFX.PlayOneShot(gunShot);
         bulletInstance.transform.Rotate(Random.Range(-bProp.spread, bProp.spread), Random.Range(-bProp.spread, bProp.spread), 0);
         bRb.AddForce(bProp.bSpeed * bulletInstance.transform.forward * Time.deltaTime);
         fireTime = bProp.fRate;
         Debug.Log(magLeft);
     }
 }

 void Reload()
 {
     magLeft = bProp.magSize;
     reloading = false;
     Debug.Log(magLeft + " lol");
 }

}