Correcting misconceptions on a few posts here:
1) IAR6940 cannot provide sustained firepower
2) IAR 6940 is not a SAW
In fact, a drum magazine can be used on the IAR6940 if needed.
The US Marine used it to replace their M249 which in itself is a very competent weapon
The only thing I found strange is that SAF is reverting to the AR15 based set up when the standard rifle is bullpup.
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The Colt IAR6940 was a squad automatic weapon designed by Phil Hinckley and manufactured by Colt's Manufacturing LLC in prototype form only. It was based on the design of the M16A4 series of rifles.
The Colt IAR was made to compete with FN HAMR and M27 Infantry Automatic Rifle for the IAR program. Three prototypes were made. Interestingly, it was better than its rivals with better cooling, ergonomic and less recoil, but it was more expensive than the M27.
The Colt IAR is chambered for the 5.56x45mm and is designed to "satisfy the role currently played by the FN M249 SAW in a lighter, more man-portable mode" at significant cost savings he SAW. It's direct gas impingement, not gas piston/op-rod. Colt went with the direct gas impingement system, has a patented Monolithic Upper Receiver with MIL-STD-1913 rails at the 12, 3, and 9 o’clock positions.