I'm obliged to Matt Bracken for republishing an article from The American Rifleman magazine's January 1969 issue. The author of that article was a Captain in the US Army at the time. He wrote it to try to counter the reams of negative publicity surrounding the then-relatively-new M16 rifle. It holds a lot of historical interest. Here are a few excerpts.
I have carried at different times 2 M16's as well as 2 of the stubby little CAR-15's. The CAR-15 is simply an M16 with a short carbine-length barrel and telescoping stock. With these 4 arms I have never experienced a jam in 18 months of combat. If given the same care as a .22 rimfire semi-automatic rifle, the M16 will not fail.
. . .
I have knocked out Communists at ranges from 50 ft. to 750 meters and have yet to use full-automatic fire ... If a group of Uncle Ho's "nephews" jump out of a clump of bamboo 10 ft. from you, go ahead and hose them with full-automatic fire, but if they are 100 feet or so away you can drop them quickly with aimed semi-automatic fire. You will be surprised how fast the trigger finger can be wiggled under combat conditions! In other than very close combat it is better to shoot straight than first.
. . .
Military regulations prohibit one from bringing personal arms to Vietnam, but do not prohibit telescope sights. I brought over a 2x-7x variable sight with internal range finder and with mount for the Colt AR-15 commercial rifle. This proved an ideal tool for the NCO or company grade officer as it eliminated the guesswork in range estimation. Additionally this scope has greater magnification than the 6x binocular with less than half its weight.
I was told by so-called experts that the M16 rifle is not accurate beyond 350 meters. But with my rifle fitted with bipod mount and scope sight and firing tracer ammunition, I can reach out and drop a walking enemy soldier at better than 700 meters range. And I make no claim to being an outstanding shot.
. . .
It is difficult to concentrate 18 months of experience in one article, but I would like to emphasize that the M16 is a great combat arm. True the ones they had 3 years ago were jam prone if not cleaned meticulously, but the improved M16A1 version now in use is tough and will take as much rough handling as either the M14 or the old M1. My M16 has never let me down.
There's more at the link.
I found the author's comments interesting, because in the 1970's South Africa tested a number of assault rifles chambered for the 5.56x45mm NATO cartridge. Among them were several early-model M16's, all of which failed miserably when subjected to African dust and dirt (not to mention the rainy season!). Based on this article, I presume that those tested were the first models of that rifle that had proven problematic in Vietnam, rather than the more developed M16A1 that the author used.
Of course, the proof of the pudding is in the eating: so the fact that the M16 and its M4-derivative carbine (in enhanced versions) remain the standard-issue US military rifles to this day, more than 50 years after that article was written, speaks for itself. It's also interesting that the US Army's newly-selected 1x-6x optical sight for its rifles and carbines is strikingly similar, in terms of power, to the privately-owned 2x-7x scope the author took to Vietnam with him. What's old is new again?