The ascendancy of the M240 SAW was brought into to provide suppressive
fire reliving the rifleman from blowing through magazines in short
order. The 3 round burst mode solved several problems with the M16,
barrel wear, burning your fingers on the gas tube and reducing the
amount of ammo that needed to get to the front-line troops.
Oh, didn't know that either. I see the burst control was added to the M16A2 version. That was smart.