need help with multifire script

I was making a script to make an automatic gun but the script i have makes it semi-automatic

this is my script

var bullitPrefab:Transform;

function Update () 
{
    if(Input.GetButtonDown("Fire1"))
    {
        var bullit = Instantiate(bullitPrefab, 
                                        GameObject.Find("spawnpoint 1").transform.position, 
                                        Quaternion.identity);
        bullit.rigidbody.AddForce(transform.forward * 3500);
    }
}

thanks

Try

`input.getbutton()`

instead of

`input.getbuttondown()`

getbuttondown only works once during the frame is was pushed.

http://unity3d.com/support/documentation/ScriptReference/Input.GetButton.html

http://unity3d.com/support/documentation/ScriptReference/Input.GetButtonDown.html