Can anyone help me out with the script???

I am trying to make an fps game. The following script is attached to bullet which is instantiated by a gun (with GunScript). I wrote the code such that it instantiates a bullet hole on both side of a wall which is penetrated by it. But it only makes it on the front side and not on the other side... I know its not a big deal, but I want to know where the problem is.

 using UnityEngine;
 using System.Collections;
 
 public class BulletScript : MonoBehaviour
 {
     public GameObject bulletHole;            // GameObject (Plane) with a bulletHole Texture
     public GameObject impactEffect;          //GameObject with impactEffect particle emmitter
 
     private float hitCount = 0f;
     private float damagePoints;
     private float impactForce;
     private float maxHits;
     private bool hasHit = false;   // To check if bullet had done max hits
     private Vector3 oldPos;
     private Vector3 newPos;
     
     void Start ()
     {
         oldPos = transform.position;
         newPos = transform.position;
     }
 
     void Update ()
     {
         if (hasHit) {
             return;
         }
         newPos = transform.position;
         Vector3 dir = newPos - oldPos;
         float dist = dir.magnitude;
         RaycastHit[] hits = Physics.RaycastAll (oldPos, dir, dist);
 
         for (int i = 0; i < hits.Length; i++)
         {
             RaycastHit hit = hits[i];
 
             newPos = hit.point;
             OnHit(hit);
             if (hitCount >= maxHits)
             {
                 hasHit = true;
                 Destroy (gameObject);
                 break;
             }
         }
 
         RaycastHit hit2;
         if (Physics.Raycast(newPos, -dir, out hit2, dist))
         {
             if (!hasHit) {
                 OnBackHit(hit2);
             }
         }
 
     }
 
     public void SetUp(float[] info)            // Setup method is called from the GunScript
     {
         damagePoints = info [0];           //Ignore this function
         impactForce = info [1];
         maxHits = info[2];
 
     }
 
     public void OnHit(RaycastHit hit)
     {
         hitCount++;
         Vector3 contactPoint = hit.point;
         Quaternion holeRotation = Quaternion.FromToRotation (Vector3.up, hit.normal);
         GameObject impactInstance = Instantiate (impactEffect, hit.point + 0.1f * hit.normal, Quaternion.FromToRotation(Vector3.up, transform.forward)) as GameObject;
         GameObject holeInstance = Instantiate (bulletHole, contactPoint, holeRotation) as GameObject;
 
         holeInstance.transform.parent = hit.transform;
 
         if (hit.rigidbody) {
             hit.rigidbody.AddForce(transform.forward * impactForce, ForceMode.Impulse);
         }
     }
 
     public void OnBackHit(RaycastHit hit)       //This method is used for creating bulletHole on other side of the penetrated wall
     {
         Vector3 contactPoint = hit.point;
         Quaternion holeRotation = Quaternion.FromToRotation (Vector3.up, hit.normal);
 
         Instantiate (impactEffect, hit.point + 0.1f * hit.normal, Quaternion.FromToRotation (Vector3.up, transform.forward));
         GameObject newHole = Instantiate (bulletHole, contactPoint, holeRotation) as GameObject;
         newHole.transform.parent = hit.transform;
     }
 }

Thanks in advance...