I think he was asking about the SIG 522 SWAT Model, .22LR NOT the 5.56. I just picked up a Brand New SIG 522 standard Black model for $409.00 The Gunshop Owner told me that SIG was offering dealers deals on the 522 with purchase of any SIG 556, so he was just passing the discount on to his customers.
The Standard 522 has a Plastic Block in the dovetail on the Front Gas Block, I'm knocking it out and putting a Aurora Front Site on it, The Picatinney Rail is made into the Upper Receiver, so at least there won't be any Screw Stud issues like on the 556. The Rail is solid, NO cutout or Flipup Rear Site, so I'm putting a Aurora rear Site on it. It uses all 556/551 furniture, replacing it with SIG Green 551 Forearm and Buttstock, 556 SIG Green Pistol Grip. It has Push Pins like the 556 Classic, may change them out for MFI SIG copies. I have a SAN SIG Bayonet Lug that I'm going to put on it. The Lower Receiver is POLYMER, Trigger Guard is molded into it, no replacing it. Looks like the magazine is a Black Dog Magazine with SIG's name on it.