The Marine Corps is only looking at an inital order of 4,000 IAR's. And half of those will be retained for testing and the other 2,000 will be tested in the field.

Hey, most Marines thought the M-1 Grand was a pos in the early 1940's. After they aquired a few from Army units on Guadacanal, they switched to the M-1 and got rid of the 03A1 bolt action Springfield as fast as they could.

The upgrade to the M-14 was easy in the early 1960's.
I saw my first M-14 and M-60 MG when the 503rd Airborne Regt. arrived on Okinawa in late 1959. The Paratroopers let us play with their new toys at a Fam-Fire exersize in the Northern Training Area on the Rock.

The Marine Divisions started getting M-14's in 1961. Then switched out to the M-16 after the Vietnam War Started.

They didn't like that shift at all.

I think you have to keep exploring the possibilities. If they can develop a solid IAR that is 6 pounds lighter, that will transfer into the ability of increase the individual AR gunner to carry more ammo, water, etc.