Adjust Line Renderer start position to follow bone rotation

Question

I'm trying to make my first game in Unity and I want a line renderer to draw from the end of a turret's gun barrel. The problem is I'm rotating 2 bones in the turret to make it look at the enemy. I've used the bounding box of the turret to calculate the offset from the turret's origin to the end of the gun barrel. But when the turret rotates this position is obviously wrong. How can I calculate the correct starting point for the line renderer after performing a rotation?

Here is the code for the rotation and the line renderer:

void Start () {
    enemyManager = GameObject.Find("EnemyManager").GetComponent<EnemyManager>();
    lazerLine = GetComponent<LineRenderer>();

    platform = transform.root.Find("Armature/BaseBone/PlatformBone"); //Get the root transform of this turret (I.e. the turret itself, not the gun barrel)
    gunBox = transform.root.FindChild("Armature/BaseBone/PlatformBone/LowerArmBone/UpperArmBone/GunBoxBone");

    gunBounds = transform.parent.GetComponent<SkinnedMeshRenderer>().bounds.size; //Get the bounding box of the turret
}

void LateUpdate()
{
    Vector3 lookAt;
    Quaternion platformRotation;
    Vector3 gunLookAt;
    Quaternion rotation;

    if (enemiesInRange.Count > 0)
    {
        //Rotate Platform (The silver platform at the base of the turret)
        lookAt = enemyManager.activeEnemies[enemiesInRange[0]].transform.position - platform.position;
        lookAt.y = 0; //0 the Y axis to stop the turret tilting up or down

        platformRotation = Quaternion.LookRotation(lookAt);

        float rotateSpeed = 10.0f * Time.deltaTime;
        platform.rotation = Quaternion.Lerp(platform.rotation, platformRotation, rotateSpeed);

        //Rotate GunBox
        gunLookAt = enemyManager.activeEnemies[enemiesInRange[0]].transform.position - gunBox.position;

        rotation = Quaternion.LookRotation(gunLookAt);
        gunBox.rotation = Quaternion.Lerp(gunBox.rotation, rotation, rotateSpeed);

    }

    if (timer <= effectsDisplayTime)
    {
        Vector3 lazerStart = transform.position;
        //Adjust the lazer to draw from the default position of the top gun barrel (using the bounding box of the turret to calculate the position)
        lazerStart.y += (gunBounds.y * 0.85f);
        lazerStart.z += (gunBounds.z / 2) + 0.05f;

        //Adjust the lazer to follow the current rotation of the gun
/* ##### This is the part I need to add ##### */

        //Draw the lazer
        lazerLine.enabled = true;
        lazerLine.SetPosition(0, lazerStart);
        lazerLine.SetPosition(1, enemyManager.activeEnemies[enemiesInRange[0]].transform.position); //Of the enemies in range, shoot the first enemy that entered the turrets range

        effectsEnabled = true;
    }
}

Here are 2 picture to give you a better idea of what's happening.

This is with the rotation code commented out.

This is with the rotation code running.

Answer 1

It might be simpler to use an empty gameobject on the tip of the barrel, with the head of your turret as its parent, and use that as a starting point for your line renderer.

EDIT: Final sollution (can be found in comments as well): Make an empty gameobject the child of the bone that controls the head of the turret. Use this as a startingpoint for the line renderer.