test.cs

var projectileCount = 3;
var initialOffset = -30;

for(int i = 0; i < projectileCount; i++) {

  var projectile = Instantiate(projectile, cam.transform.position, cam.transform.rotation * Quaternion.Euler(0,initialOffset,0));
  initalOffset += 30;
    
  projectile.GetComponent<Rigidbody>().AddForce(projectile.transform.forward * 15, ForceMode.Impulse);
}