The first time I fired a M14 was an eye opener.
Absolutely!
this is one of the myths of machine guns: that only the first shot is controllable. It all comes down to proper machine gun shooting technique.
It's a myth, only in the fact that it is not 100% true. For most people, it is 100% true, simply because most people don't know, or get to learn the techniques to compensate for the recoil.
Another myth, one so entrenched that it is "common knowledge" is how the muzzle of a Tommygun climbs, no matter what you do...
it does not. Muzzle climb (and drift to the side) is the result of the SHOOTER, not the gun itself.
I was in the last class USAOC&S trained on the M14 rifle (1975). Our "final exam" was to draw one of the test weapons (which had known defects), inspect, repair, and test fire them. 15rounds, 5 semi auto, 10 full auto.
The test range was a firing port in the wall about a foot square, at about knee height, so you had to be kneeling or sitting to get the rifle in the port.
I was not the first one finished, and listened to 3 or 4 others firing, and noted that on full auto, they were all firing 2 shot bursts. I was young, had owned a couple of .308Win bolt guns, (lighter than the M14 by a considerable amount) and figured I could handle the recoil. I had fired the m16A1 on full auto, and the M60 in basic training.
I was cocky, and decided I would pull off a 3 round burst, when my turn came. When it was my turn, I was given a mag with 15 rnds, and told 5 rounds semi, 10 full auto, short bursts.
My "3 rnd" burst was 6 rounds. Despite what I thought I knew, I got taught a lesson. My "short burst" moved me from the kneeling to the sitting position! However, my rifle NEVER left the firing port. The instructor glared at me, and said "SHORT BURSTS!!!". My remaining 4 rnds were two 2rnd bursts.
The M14 got a reputation (actually deserved) for being uncontrollable in FA fire, because of the people using it, its light weight (for FA fire in that caliber), and its high cyclic rate.
"Experts" couldn't keep it on a 25M target on full auto. True. But remember that at the time, there were very, very few "experts" that had experience firing that light a weapon in that heavy a caliber full auto.
While I no longer remember who did it, I did see a "modified" M14 gas system that brought the cyclic rate down to around 600RPM or so, and the gun was quite controllable in full auto. And, of course, it was civilians who came up with it. The military never had an interest in it, because the powers that be (at the time) committed us to the M16, from now, and henceforth, forever...
(or until someone comes up with something demonstrably better & cheaper...)