You had an M-14E2 or A1, right? You might be interested in one of the videos at my post 105 above.
The horizontal carriage allowed us to fire immediately from the waist if we ran into an ambush and it also allowed fast entry into the prone.
Your videos are cool but very civilian: there's never any reason to fire full-auto from the offhand (standing) position in combat. Full auto is almost always fired from the prone, which is what you'd better be if the first rounds the enemy fired haven't already got you. I have no idea why our YouTube cowboys think that that is way we employed them - but of course, they would be difficult to control.
I was as a 21 year old Lance Corporal that had a relatively free hand in picking a weapon to keep me alive and I was very happy with my '14. It was accurate - I successfully engaged an enemy sniper at 600m - and it was controllable and exceptionally dependable in an environment that was always hot, wet, and filthy. I could reliably keep a 3-4 round burst with the size of a human body at 150m+. Don't need to ask me how I know that.
As I said earlier, when I was wounded in May '67, there was a fast grab for my M-14. It was the best weapon for many miles around.