I have the same question.
Plus, I noticed that the newer "SWAT" 522 has quad rail. But I am not sure if it's the same as the one on SWAT 556. The one on 556 is sold at $300ish, so I think more likely the one on 522 is different--nobody would put a $300 rail on a $600 gun.  
Plus, I noticed that the newer "SWAT" 522 has quad rail. But I am not sure if it's the same as the one on SWAT 556. The one on 556 is sold at $300ish, so I think more likely the one on 522 is different--nobody would put a $300 rail on a $600 gun.