I came home from Viet Nam with a prejudice against the AR-style rifles. They were not, IME, nearly as accurate at the M-14.
I did see Marines with the little Colt scope, sitting on the bank of the River and getting hits across it at Hue during Tet, but I attributed it to the scope. It was the first time I'd ever seen a scope on an M-16.
I had trained with the M-14 and the M-16 came later. Little or no training given.
It just wasn't very accurate.
Of course, I recall that young Marine breaking the metal band on the C-Rats during Tet with the prongs of the flash hider-Gee, could that have been a cause of the inaccuracy? Later, we learned that such things bent the barrel! Imagine that!
I'm told that was one of the reasons they modified the M-16 to have the bird-cage flash hider.
So, when the rifle bug hit, I bought the finest of Match ready M-1s or M-1As or had them built.
They were all superbly accurate, would shoot an inch or perhaps just a little less at a 100 yards all day long. Unless it rained or was real humid. Then they became less accurate.
Finally, I bought a Colt Match H-Bar. This was early on, when they first came out. Sent it to Frank White who "accurized" it.
Wow! What a difference!
Since then I have had several that would shoot a half inch or less at a 100 yards and didn't care if it was wet, humid, cold or just right.
I still like the old M-1 and M-1A. But, if I was wanting something to shoot and get hits every time (why else would I have it), I'd get a RRA or something similar.
Bob