For all you CheyTac fanboy-types, a less expensive one now exists(this might be old news):
http://www.airsoftglobal.com/shop/index.php?main_page=product_info&cPath=552_557&products_id=14322&zenid=8tmr82tlhb7a6cb1qtepi1uqu2
http://www.airsoftglobal.com/shop/index.php?main_page=product_info&cPath=552_557&products_id=14322&zenid=8tmr82tlhb7a6cb1qtepi1uqu2