Why is my projectile firing "off" after rotation

I have a simple 3D object inside of a nulll object. The null object has a script to instatiate and launch/fire a projectile. It's a placeholder space fighter while I test.

When pointing forward at game load, I can fire straight forward without issues, but if I rotate to a side, the origin of the projectiles turns quicker than the craft.

Code

 void Fire()
     {
         GameObject projectileInstance = Instantiate(Projectile, transform.position, transform.rotation);
         projectileInstance.GetComponent<Rigidbody>().AddRelativeForce(transform.forward * SpeedMultiplier, ForceMode.VelocityChange);
     }

I want to fire the objects straight ahead at all times