No first hand experience in the Sandbox, but the shooting by our guys that is shown on various videos, all I see is somewhat aimed, suppressive fire and quick mag changes.
I understand the attraction of small caliber rifle ammo to grunts, we were all amazed how much 5.56 equaled 5-6 loaded M-14 20 round magazines. Made you feel well equipped.
But, low recoil rifles and tons of ammo make "somewhat aimed, suppressive fire" attractive, rather than precision elimination of targets with slow fire?