instansiating prefab, then adding force in camera direction C#

hey guys . would appriaiate any hand with this code. cant seem to get it to work. the gui at the bottom is just a force indicator. i want to be able to throw a ball in the direction the fps camera is looking

 public class FireProjectile : MonoBehaviour {
 
     
     public GameObject projectile;
     public float force = 0;
     
     // Update is called once per frame
     void Update () 
     {
         if (Input.GetButton("Fire1"))
         {
             force += 20 * Time.deltaTime;
         }
         if (Input.GetButtonUp("Fire1"))
         {
              projectile.rigidbody.AddForce(Camera.main.transform.right * force);
             GameObject pro =  Instantiate(projectile,transform.position, Quaternion.identity) as GameObject;
                     
             
             force = 0;
             
         }
     
     }
     
     void OnGUI()
 {
     string forceText = GUILayout.TextField(force.ToString("0.00"));
  
     float newForce;
     if (float.TryParse(forceText, out newForce))
     {
         force = newForce;
     }
 }
     
 }