sending message to bullet (javascript)

So either hold on to the value of shot in a variable attached to the script, rather than a local variable or turn the whole thing into a coroutine.

 #pragma strict
  
 var ammo : int;
 var shot : GameObject;
 var maxAmmo : int;
 var charge : float;
 var damage : int;
 var force : int;
 var projectile : GameObject;
 var fireRate = 0.5;
 var nextFire = 0.0;
 var accuracy : int;
 var loaded : boolean;
  
 function Start () {
  
 }
  
 function Update () 
 {
     if (Input.GetButtonDown ("Fire1") && Time.time > nextFire && ammo > 0) //make bullet
     {
         ammo--;
         shot = Instantiate (projectile, transform.position, Quaternion.Euler(Vector3(transform.eulerAngles.x+Random.Range(0,accuracy), transform.eulerAngles.y+Random.Range(0,accuracy), transform.eulerAngles.z+Random.Range(0,accuracy))));
         loaded = true;
     }
     if(Input.GetButton ("Fire1") && loaded) //charge while holding mouse
     {
         // send this message to shot somehow.
         shot.SendMessage("Charge", SendMessageOptions.DontRequireReceiver);
     }
     if (Input.GetButtonUp ("Fire1") && loaded) //release bullet
     {
         nextFire = Time.time + fireRate;
         loaded = false;
  
     }
  
 }

or like this:

  function Shoot()
  {
             ammo--;
             var shot = Instantiate (projectile, transform.position, Quaternion.Euler(Vector3(transform.eulerAngles.x+Random.Range(0,accuracy), transform.eulerAngles.y+Random.Range(0,accuracy), transform.eulerAngles.z+Random.Range(0,accuracy))));
             while(Input.GetButton ("Fire1"))
             {
                  shot.SendMessage("Charge", SendMessageOptions.DontRequireReceiver);
                  yield;
             }
             nextFire = Time.time + fireRate;
  }

  function Update()
  {
       if (Input.GetButtonDown ("Fire1") && Time.time > nextFire && ammo > 0)
       {
          Shoot();
       }
  }