Task & Purpose explains why the US Special Forces switched to the FN SCAR rifle in this video... "While the SCAR-Light and -Heavy were designed and built in tandem, their performance and service histories diverged in 2010. The weapons were mostly living up to the hype but there were some early teething issues holding them back. Every weapon runs into this teething problems but what makes the difference between success and failure is how easy it is to correct these early problems. In the case of the SCAR, the Light version named the MK 16 had the misfortune of having more issues and less capability advances than its heavier MK17 version."