var range = 100.0;
var fireRate = 0.05;
var force = 10.0;
var damage = 5.0;
var bulletsPerClip = 40;
var clips = 20;
var reloadTime = 0.5;
private var hitParticles : ParticleEmitter;
var muzzleFlash : Renderer;
var bulletsLeft : int = 0;
private var nextFireTime = 0.0;
private var m_LastFrameShot = -1;
function Start ()
{
    hitParticles = GetComponentInChildren ( ParticleEmitter );
// We don't want to emit particles all the time, only when we hit something.

    if ( hitParticles )

        hitParticles.emit = false;

    bulletsLeft = bulletsPerClip;
}

function Update()
{
    if ( Input.GetButtonDown ( "Fire1" ) )
    {
        FireOneShot();
    }
}

function LateUpdate()
{
    if ( muzzleFlash )
    {
// We shot this frame, enable the muzzle flash
        if ( m_LastFrameShot == Time.frameCount )
        {
            muzzleFlash.transform.localRotation =
                Quaternion.AngleAxis ( Random.Range ( 0, 359 ), Vector3.forward );
            muzzleFlash.enabled = true;

            if ( audio )
            {
                if ( !audio.isPlaying )
                    audio.Play();

                audio.loop = true;
            }
        }

// We didn't, disable the muzzle flash

        else
        {
            muzzleFlash.enabled = false;
            enabled = false;
// Play sound

            if ( audio )
            {
                audio.loop = false;
            }
        }
    }
}

function Fire ()
{
    if ( bulletsLeft == 0 )
        return;

// If there is more than one bullet between the last and this frame
// Reset the nextFireTime
    if ( Time.time - fireRate > nextFireTime )
        nextFireTime = Time.time - Time.deltaTime;

// Keep firing until we used up the fire time
    while ( nextFireTime < Time.time && bulletsLeft != 0 )
    {
        FireOneShot();
        nextFireTime += fireRate;
    }
}

function FireOneShot ()
{
    var direction = transform.TransformDirection ( Vector3.forward );
    var hit : RaycastHit;
// Did we hit anything?

    if ( Physics.Raycast ( transform.position, direction, hit, range ) )
    {
// Apply a force to the rigidbody we hit
        if ( hit.rigidbody )
            hit.rigidbody.AddForceAtPosition ( force * direction, hit.point );

// Place the particle system for spawing out of place where we hit the surface!
// And spawn a couple of particles
        if ( hitParticles )
        {
            hitParticles.transform.position = hit.point;
            hitParticles.transform.rotation =
                Quaternion.FromToRotation ( Vector3.up, hit.normal );
            hitParticles.Emit();
        }

// Send a damage message to the hit object
        hit.collider.SendMessageUpwards ( "ApplyDamage", damage,
                                          SendMessageOptions.DontRequireReceiver );
    }

    bulletsLeft--;

// Register that we shot this frame,
// so that the LateUpdate function enabled the muzzleflash renderer for one frame
    m_LastFrameShot = Time.frameCount;
    enabled = true;
// Reload gun in reload Time

    if ( bulletsLeft == 0 )
        Reload();
}

function Reload ()
{
// Wait for reload time first - then add more bullets!
    yield WaitForSeconds ( reloadTime );
// We have a clip left reload

    if ( clips > 0 )
    {
        clips--;
        bulletsLeft = bulletsPerClip;
    }
}

function GetBulletsLeft ()
{
    return bulletsLeft;
}

This isn't changed, just better formatting...

Where are you spawning/creating/instantiating the prefab/bullet? Sorry, not seeing it... When it does FireOneShot(); when you click, it makes the direction, and a raycast... Aplies a force if it hits something, and spawns some particles, then it takes away damage from that item if possible.. Finally it takes out some bullets, checks if their is no bullets, if so, they reload.... Their isn't any bullet.. Am I right?

Also, maybe you don't want a visual bullet, then in that case, you have to make the particle system to use for the ParticleEmmiter up top...

Hope that helps!