The problems with the M-16 in Vietnam were attributed to Winchester changing the powder without bothering to tell anyone. The gun and round were designed to use ball powder, W-W changed to an extruded powder to save a few pennies and it was a disaster, the guns got gummy much faster, and the cleaning kits for them hadn't even been issued to the troops in many cases. Once the bugs were worked out, it ran fine. While the AK is indeed a fine weapon, and designed to work under field conditions, the M-16 was a far better weapon in accuracy and lethality.
At the same time, I'm enthusiastic about the 6.8SPC. A better bullet design, better long-range effectiveness, and enhanced lethality at all ranges. Too bad they didn't have them at Mogadishu, that might have ended much better if our troops weren't shooting AP bullets into human targets that barely noticed being hit!
PJ