GameObject Instantiated in Wrong Position

Hi,

I'm making a gun system, and when I click I instantiate a bullet with the player position, the problem is that:

 //BulletScript attached to the bullet Gameobject
 
 using UnityEngine;
 using System.Collections;
 
 public class BulletScript : MonoBehaviour {
 
     // Use this for initialization
     void Start () {
         float x = GameObject.Find("Player").transform.FindChild("mainCam").transform.position.x+3;
         float y = GameObject.Find("Player").transform.FindChild("mainCam").transform.position.y;
         float z = GameObject.Find("Player").transform.FindChild("mainCam").transform.position.z+3;
         transform.position = new Vector3(x, y, z);
     }
     
     // Update is called once per frame
     void Update () {
         transform.rigidbody.AddForce(transform.eulerAngles*10);
     }
 }

And the second script:

 //GunScript attached to the Inventory Item (it's a MP5)
 
 using UnityEngine;
 using System.Collections;
 
 public class GunScript : MonoBehaviour {
 
     GameObject bullet;
     
     // Use this for initialization
     void Start () {
         if(Input.GetMouseButtonDown(0)) { //This is weird because I have to use it in the Start void, and not in the Update
             bullet = GameObject.Instantiate(Resources.Load("Models/Items/Bullets/bala"), GameObject.Find("Player").transform.FindChild("mainCam").transform.position, GameObject.Find("Player").transform.FindChild("mainCam").transform.rotation) as GameObject;
         }
     }
     
     // Update is called once per frame
     void Update () {
 
     }
     
 }
 

How can I solve that?

Thanks in advance. Bye.