You guys make me chuckle when you go on and on about perceived problems with the M-14's "weight" and "controllability ... it weighs only a few ounces more and is just as accurate in semi-auto as the M-1 Garand that a bunch of "average" draftees used 60 years ago to win a World War ...
Yeah, when comparing the M1 and M14, there are a few differences but all in all they are pretty much the same rifle. As I'm sure you know, the M14 was the intention of having a full auto capable rifle that mimicked the performance of the M1. Combining that with the weight and recoil of the 7.62, it created an issue in controllability when at full auto.
Now, that said, I too was taught by my first rangemaster that going full auto is only for fun on the range or if you're all out of other options. However, that's part of why the M16 came on line, b/c back then it was perceived that full auto on the average serviceman's rifle would be a good thing.
I heard once that in the mid-70's there was some discussion on switching the M16 to either a semi-auto or three or four round burst mode, because so many guys were just going to full auto and randomly pointing and holding the trigger, just wasting ammo instead of putting rounds on target. If that's true it definitely makes sense.
Either way, do I think that the average serviceman could handle an M14? Yeah, probably, as you said the M1 has been used by thousands and the 7.62, in my opinion, feels slightly less in recoil than the .30 (at least to me). However, I think that at the time the M16 was coming on line the full auto option was a huge consideration, so the controllability issue was a factor.