It don't know for certain if it is safe to do so, but I would have a hard time imagining it wasn't. The pistol was designed with the FBI in mind, and so dry firing was likely considered. If no one else has a better answer, then either contact S&W, or just use snap caps.
dry fire will absolutly not harm a smith auto (centerfire). In fact it will make the trigger smooth out much like breaking in a car engine. I personally will not do a trigger job on any gun that has not been fired or dry fired at least 500 times.