Problem setting the parent.

Hi,

I have a problem setting the parent of an instiated prefab. I am working on a random weapon generator, like the one from Borderlands. When I create a weapon, it creates an empty game object prefab, with the following script attached to it, and a rigidbody. The problem is that I get an NullReference when I try to parent the weapon-part prefabs. These are just models with a collider. Any ideas or hints how I can do this? Thanks in advance! PS. I am not a great programmer, just a beginner.

 using UnityEngine;
 using System.Collections;
 
 public class Creator : MonoBehaviour {
 
     public Transform weaponBodyPref1;
     public Transform weaponBodyPref2;
     public GameObject weaponBody;
 
     public Transform weaponGripPref1;
     public Transform weaponGripPref2;
     public GameObject weaponGrip;
     
     public Transform weaponBarrelPref1;
     public Transform weaponBarrelPref2;
     public GameObject weaponBarrel;
     
     public Transform weaponStockPref1;
     public Transform weaponStockPref2;
     public GameObject weaponStock;
     
     public Transform weaponMagPref1;
     public Transform weaponMagPref2;
     public GameObject weaponMag;
     
     public Transform weaponSightPref1;
     public Transform weaponSightPref2;
     public GameObject weaponSight;
     
     
     // Use this for initialization
     void Start () 
     {
         createModel();
     }
     
     
     // Update is called once per frame
     void Update () 
     {
         
     }
     
     void createModel()
     {
         //Location
         Vector3 WeapLoc = new Vector3(this.transform.position.x, this.transform.position.y, this.transform.position.z);
         
         //Weapon Barrel
         int weaponBarrelRarity = Random.Range(0, 100);
         
         if(weaponBarrelRarity >= 0 && weaponBarrelRarity <= 29)
         {
             weaponBarrel = Instantiate(weaponBarrelPref1, WeapLoc, Quaternion.identity) as GameObject;
             Debug.Log("Barrel 1");
         }
         else if(weaponBarrelRarity >= 30 && weaponBarrelRarity <= 100)
         {
             weaponBarrel = Instantiate(weaponBarrelPref2, WeapLoc, Quaternion.identity) as GameObject;
             Debug.Log("Barrel 2");
         }
         
         //Weapon Body
         int weaponBodyRarity = Random.Range(0, 100);
         
         if(weaponBodyRarity >= 0 && weaponBodyRarity <= 29)
         {
             weaponBody = Instantiate(weaponBodyPref1, WeapLoc, Quaternion.identity) as GameObject;
             Debug.Log("Body 1");
         }
         else if(weaponBodyRarity >= 30 && weaponBodyRarity <= 100)
         {
             weaponBody = Instantiate(weaponBodyPref2, WeapLoc, Quaternion.identity) as GameObject;
             Debug.Log("Body 2");
         }
         
         //Weapon Grip
         int weaponGripRarity = Random.Range(0, 100);
         
         if(weaponGripRarity >= 0 && weaponGripRarity <= 29)
         {
             weaponGrip = Instantiate(weaponGripPref1, WeapLoc, Quaternion.identity) as GameObject;
             Debug.Log("Grip 1");
         }
         else if(weaponGripRarity >= 30 && weaponGripRarity <= 100)
         {
             weaponGrip = Instantiate(weaponGripPref2, WeapLoc, Quaternion.identity) as GameObject;
             Debug.Log("Grip    2");
         }
         
         //Weapon Stock
         int weaponStockRarity = Random.Range(0, 100);
         
         if(weaponStockRarity >= 0 && weaponStockRarity <= 29)
         {
             weaponStock = Instantiate(weaponStockPref1, WeapLoc, Quaternion.identity) as GameObject;
             Debug.Log("Stock 1");
         }
         else if(weaponStockRarity >= 30 && weaponStockRarity <= 100)
         {
             weaponStock = Instantiate(weaponStockPref2, WeapLoc, Quaternion.identity) as GameObject;
             Debug.Log("Stock     2");
         }
         
         //Weapon Mag
         int weaponMagRarity = Random.Range(0, 100);
         
         if(weaponMagRarity >= 0 && weaponMagRarity <= 29)
         {
             weaponMag = Instantiate(weaponMagPref1, WeapLoc, Quaternion.identity) as GameObject;
             Debug.Log("Mag 1");
         }
         else if(weaponMagRarity >= 30 && weaponMagRarity <= 100)
         {
             weaponMag = Instantiate(weaponMagPref2, WeapLoc, Quaternion.identity) as GameObject;
             Debug.Log("Mag 2");
         }
         
         //Weapon Sight
         int weaponSightRarity = Random.Range(0, 100);
         
         if(weaponSightRarity >= 0 && weaponSightRarity <= 29)
         {
             weaponSight = Instantiate(weaponSightPref1, WeapLoc, Quaternion.identity) as GameObject;
             Debug.Log("Sight 1");
         }
         else if(weaponSightRarity >= 30 && weaponSightRarity <= 100)
         {
             weaponSight = Instantiate(weaponSightPref2, WeapLoc, Quaternion.identity) as GameObject;
             Debug.Log("Sight 2");
         }
         
         GameObject mainWeap = GameObject.Find("newSMG(clone)");
         weaponBody.gameObject.transform.parent = mainWeap.gameObject.transform;
         weaponGrip.gameObject.transform.parent = mainWeap.gameObject.transform;
         weaponMag.gameObject.transform.parent = mainWeap.gameObject.transform;
         weaponBarrel.gameObject.transform.parent = mainWeap.gameObject.transform;
         weaponStock.gameObject.transform.parent = mainWeap.gameObject.transform;
         weaponSight.gameObject.transform.parent = mainWeap.gameObject.transform;
         
     
     }
 }

I have updated the script to the most recent version (added all the weapon parts and tried various methods for the parenting), but I still can't figure out the answer. Please help me out!