Fire Line Renderer from Camera

I'm looking to fire a Line Renderer from my Camera into space. (I'm using an ARCamera)

I've got it doing so but it's not working how I'd like; its firing into the distance towards the centre of the screen which is perfect, but the origin point (ARCamera) differs each time I fire. I've tried applying the Line Renderer and relating script to a Cube as a child of the ARCamera but it still doesnt work properly.

I initially thought it could be because the ARCamera is always moving, but even when I keep it perfectly still, I have the same problem.

Here is the script I'm using:

 using UnityEngine;
 
 public class PlayerShooting : MonoBehaviour
 {
     public int damagePerShot = 20;                  // The damage inflicted by each bullet.
     public float timeBetweenBullets = 0.15f;        // The time between each shot.
     public float range = 100f;                      // The distance the gun can fire.
     
     float timer;                                    // A timer to determine when to fire.
     Ray shootRay;                                   // A ray from the gun end forwards.
     RaycastHit shootHit;                            // A raycast hit to get information about what was hit.
     int shootableMask;                              // A layer mask so the raycast only hits things on the shootable layer.
     ParticleSystem gunParticles;                    // Reference to the particle system.
     LineRenderer gunLine;                           // Reference to the line renderer.
     AudioSource gunAudio;                           // Reference to the audio source.
     Light gunLight;                                 // Reference to the light component.
     float effectsDisplayTime = 0.2f;                // The proportion of the timeBetweenBullets that the effects will display for.
     
     void Awake ()
     {
         // Create a layer mask for the Shootable layer.
         shootableMask = LayerMask.GetMask ("Shootable");
         
         // Set up the references.
         gunParticles = GetComponent<ParticleSystem> ();
         gunLine = GetComponent <LineRenderer> ();
         gunAudio = GetComponent<AudioSource> ();
         gunLight = GetComponent<Light> ();
     }
     
     void Update ()
     {
         // Add the time since Update was last called to the timer.
         timer += Time.deltaTime;
         
         // If the Fire1 button is being press and it's time to fire...
         if(Input.GetButton ("Fire1") && timer >= timeBetweenBullets)
         {
             // ... shoot the gun.
             Shoot ();
         }
         
         // If the timer has exceeded the proportion of timeBetweenBullets that the effects should be displayed for...
         if(timer >= timeBetweenBullets * effectsDisplayTime)
         {
             // ... disable the effects.
             DisableEffects ();
         }
     }
     
     public void DisableEffects ()
     {
         // Disable the line renderer and the light.
         gunLine.enabled = false;
         gunLight.enabled = false;
     }
     
     void Shoot ()
     {
         // Reset the timer.
         timer = 0f;
         
         // Play the gun shot audioclip.
         gunAudio.Play ();
         
         // Enable the light.
         gunLight.enabled = true;
         
         // Stop the particles from playing if they were, then start the particles.
         gunParticles.Stop ();
         gunParticles.Play ();
         
         // Enable the line renderer and set it's first position to be the end of the gun.
         gunLine.enabled = true;
         gunLine.SetPosition (0, transform.position);
         
         // Set the shootRay so that it starts at the end of the gun and points forward from the barrel.
         shootRay.origin = transform.position;
         shootRay.direction = transform.forward;
         
         // Perform the raycast against gameobjects on the shootable layer and if it hits something...
         if(Physics.Raycast (shootRay, out shootHit, range, shootableMask))
         {
             // Try and find an EnemyHealth script on the gameobject hit.
             EnemyHealth enemyHealth = shootHit.collider.GetComponent <EnemyHealth> ();
             
             // If the EnemyHealth component exist...
             if(enemyHealth != null)
             {
                 // ... the enemy should take damage.
                 enemyHealth.TakeDamage (damagePerShot, shootHit.point);
             }
             
             // Set the second position of the line renderer to the point the raycast hit.
             gunLine.SetPosition (1, shootHit.point);
         }
         // If the raycast didn't hit anything on the shootable layer...
         else
         {
             // ... set the second position of the line renderer to the fullest extent of the gun's range.
             gunLine.SetPosition (1, shootRay.origin + shootRay.direction * range);
         }
     }
 }

Has anyone else had this problem or know how to fix it?