I don't have any tutorial for you, but you might want to try something like this: C#

    int count = 8;
    bool reloading = false;

    void Update()
    {
       if (Input.GetKeyDown(KeyCode.R))
         Reload();

       // Should only be able to shoot if we aren't reloading and still have ammo.
       if (!reloading && count > 0 && Input.GetButtonDown("Fire1"))
         Shoot();
    }

    void Shoot()
    {
       // Do shooting stuff.
       --count;

       // If we used our last shot, then we should reload.
       if (count <= 0)
         Reload();
    }

    void Reload()
    {
       reloading = true;

       // Do reloading stuff.
       count = 8;

       reloading = false;
    }

JavaScript Version:

var count : int = 8;
var reloading : boolean = false;

function Update()
{
    if (Input.GetKeyDown(KeyCode.R))
        Reload();

    // Should only be able to shoot if we aren't reloading and still have ammo.
    if (!reloading && count > 0 && Input.GetButtonDown("Fire1"))
        Shoot();
}

function Shoot()
{
    // Do shooting stuff.
    count--;

    // If we used our last shot, then we should reload.
    if (count <= 0)
        Reload();
}

function Reload()
{
    reloading = true;

    // Do reloading stuff.
    count = 8;

    reloading = false;
}

Hope it helps :)