from:
http://kitup.military.com/2010/06/socom-cancels-mk-16-scar.html
Two well-informed industry analysts tell me that SCAR-maker FNH-USA will try to sell SOCOM on the idea of a Mk-17 common receiver that can be turned into a 5.56 or other caliber by switching out part of the lower receiver. So FNH-USA is positioning itself to rescue the Mk-16 through the Mk-17. But there’s no indication that SOCOM is biting.
http://i0.kym-cdn.com/photos/images/original/000/363/834/d00.gif