Here’s what I remember... Vietnam maximum ranges were WWII minimum ranges. Vietnam was a different environment than the Mideast and the Mideast has buildings made of concrete and the 5.56 is not an effective round to penetrate.
The M14 however, penetrated heavy vegetation, concrete gravestones, sandbags, and of course, people. Every single man I hit with my M14 went down and stayed down.
I will always despise the people who forced the idiot M16 on us when our lives depended on it.