Procurement info is pretty available. AFAIK, the SCAR is not fielded except for evaluation. I honestly don't keep up with the stuff. I just know for certainty that the HK 416 won the contracts and is actually deployable outside of evaluation.
"Late in 2004 USSOCOM announced, that the winner for the initial SCAR contracts is the FN USA, an US-based subsidiary of the famous Belgian company Fabrique Nationale Herstal. prototype rifles were manufactured by FN Manufacturing Inc, US-based subsidiary to FN Herstal; This company will also handle series production of rifles. Starting mid-2005, first SCAR rifles went to end users in US Special Operation Forces. Since USSOCOM uses Navy-type "mark" designations, SCAR rifles were officially designated as 5.56mm Rifle Mark 16 (SCAR-L / Light) and 7.62mm Rifle Mark 17 (SCAR-H/ Heavy).It is believed that Mk.16 and Mk.17 rifles will gradually replace most rifle systems now in service with US SOCOM forces, such as M4 carbines, M16 rifles, M14 rifles and Mk. 25 sniper rifles."
"On June 25, 2010 SOCOM announced that it was canceling the acquisition of the MK-16 citing limited funds and a lack of enough of a performance difference in another 5.56mm rifle to justify the purchase. Remaining funds would be expended for the MK-17 7.62x51 mm version and the MK-20 sniper variant.[24] "FNH USA believes the issue is not whether the SCAR, and specifically the [originally contracted] MK 16 variant, is the superior weapon system available today
it has already been proven to be just that, ...recently passing Milestone C and determined to be operationally effective / operationally suitable (OE/OS) for fielding. The issue is whether or not the requirement for a 5.56mm replacement outweighs the numerous other requirements competing for the customers limited budget. That is a question that will only be determined by the customer." [25] FN Herstal though has stated that the 5.56mm variant will be retained by SOCOM, and that "The choice between the 5.56 and the 7.62 caliber will be left to the discretion of each constitutive component of USSOCOM's Joint Command (e.g. SEALs, Rangers, Army Special Forces, MARSOC, AFSOC) depending on their specific missions on today's battlefield." [26]"
SCAR fielded for SOF since 2009
http://www.fnhusa.com/le/press/detail.asp?id=82
http://en.wikipedia.org/wiki/FN_SCAR
http://www.fnhusa.com/mil/scar.asp