FNH USA’s Executive Vice President of Military Operations Mark Cherpes explained to Shooting Illustrated what was going on with the FN SCAR at USSOCOM. USSOCOM could not make their mind up, but finally decided they wanted a multi-caliber system, which is why the Mk.16 is being phased out and the Mk.17 with conversion kit is being adopted.

Mark Cherpes says …

FN had proposed and offered a single-platform system to USSOCOM that would adapt via conversion kit to SOF current and future ammunition. During the requirements finalization phase, the SOF operators took the decision that the weapon should be split in two platforms, one gun for 5.56 and a second gun for 7.62. The reason this decision was made at the time is that the SOF operators did not like the fact that the 5.56 base platform would have an increase in weight over the M4. The weight difference between the MK 16 Standard and the SCAR H Standard is about half a pound.