I had just the opposite experience with the 14. When I first used it, I was about 5'6"/130 lbs. Our instructor told us to fire three round bursts and start with a clean target. Fire one burst, aiming at the lower left corner of the target. Watch what direction the rounds "climbed." Each person was a bit different, based on height and strength. Do that a couple times to get an idea where the second and third rounds would go, then always aim so your second round would hit close to dead center. After a while, we could all get the second rounds within a couple inches (or closer) of the bulls-eye every time and our three round groups even started getting closer together. I was "lucky" I wasn't very strong as most of my "climb" was vertical. About half the time, I could put three rounds in the targets' 1) right hip, 2) right/center torso, and 3) left shoulder. (This was as seen from the targets' PoV, as if they were enemies facing me, as the muzzle climbed up and to my right.) I would get two of three in the target, the remainder of the time.
At the time I was back from a partial tour in Vietnam, as a crew chief/ door gunner, I was pretty familiar with MG techniques .
I was firing from the prone, no bipod. I just wasn't impressed by it's abilities on full auto.
But maybe it was just me.
I remember thinking if I had that a few months before in the chopper, I'd have left it on semi-auto.