Mathf.Lerp with UI Slider to show reload time.

Hi!

I'm just about finished with the TANKS! tutorial, and wanted to add a few things to the TankShooting script. First I added a 1 second cooldown to the tank shots, but without any visual indication. Now I want to add a slider to visually represent this reload time. I have the slider UI as a child in the prefab canvas, and it works, but only for the first shot.

 using UnityEngine;
 using UnityEngine.UI;
 
 public class TankShooting : MonoBehaviour
 {
     public int m_PlayerNumber = 1;       
     public Rigidbody m_Shell;            
     public Transform m_FireTransform;    
     public Slider m_AimSlider; 
     public Slider m_ReloadSlider;
     public AudioSource m_ShootingAudio;  
     public AudioClip m_ChargingClip;     
     public AudioClip m_FireClip;
     public float timeBetweenShells = 1f;
     public float minReload = 0f;
     public float m_MinLaunchForce = 15f; 
     public float m_MaxLaunchForce = 30f; 
     public float m_MaxChargeTime = 0.75f;
     public float nextFire = 0f;
 
     private string m_FireButton;         
     private float m_CurrentLaunchForce;  
     private float m_ChargeSpeed;         
     private bool m_Fired;
 //    static float t = 0f;
 
 
     private void OnEnable()
     {
         m_CurrentLaunchForce = m_MinLaunchForce;
         m_AimSlider.value = m_MinLaunchForce;
 //        m_ReloadSlider.value = timeBetweenShells;
     }
         
 
     private void Start()
     {
         m_FireButton = "Fire" + m_PlayerNumber;
 
         m_ChargeSpeed = (m_MaxLaunchForce - m_MinLaunchForce) / m_MaxChargeTime;
     }
     
 
     private void Update()
     {
         
         nextFire += Time.deltaTime;
 
 /*        
         if (m_Fired == true)
         {
         m_ReloadSlider.value = Mathf.Lerp (minReload, timeBetweenShells, t);
         t += 1f * Time.deltaTime;
         }
 */
         if (nextFire > timeBetweenShells) 
         {
             m_AimSlider.value = m_MinLaunchForce;
 
             if (m_CurrentLaunchForce >= m_MaxLaunchForce && !m_Fired) 
             {
                 m_CurrentLaunchForce = m_MaxLaunchForce;
                 Fire ();
             } 
             else if (Input.GetButtonDown (m_FireButton)) 
             {
                 m_Fired = false;
                 m_CurrentLaunchForce = m_MinLaunchForce;
 
                 m_ShootingAudio.clip = m_ChargingClip;
                 m_ShootingAudio.Play ();
             } 
             else if (Input.GetButton (m_FireButton) && !m_Fired) 
             {
                 m_CurrentLaunchForce += m_ChargeSpeed * Time.deltaTime;
 
                 m_AimSlider.value = m_CurrentLaunchForce;
             } 
             else if (Input.GetButtonUp (m_FireButton) && !m_Fired) 
             {
                 Fire ();
             }
         }
     }
 
     private void Fire()
     {
         nextFire = 0f;
 
         m_Fired = true;
 
         Rigidbody shellInstance = Instantiate (m_Shell, m_FireTransform.position, m_FireTransform.rotation) as Rigidbody; 
 
         shellInstance.velocity = m_CurrentLaunchForce * m_FireTransform.forward;
 
         m_ShootingAudio.clip = m_FireClip;
         m_ShootingAudio.Play ();
 
         m_CurrentLaunchForce = m_MinLaunchForce;
     }
 }

The commented lines with Mathf.Lerp is the line that works, but only for the first shot.

What am I missing here?