The M16 made a certain amount of sense in a jungle war in which you saw the enemy from 50’ away. In wars in mountain and desert terrain, it is problematical, and that’s aside from the question of having exhaust gas blowing straight back into bolt carrier parts. People who collect guns should have one of them; for an only gun, I’d not consider it.
I have ONE black rifle. I selected a configuration that would be suitable for my son to maintain his proficiency for the USMC. I prefer a good bolt action with quality glass on top. My bolt action has a 1:9 rifling so it eats the same ammo as the black rifle.
I would think you would want a shotgun for that kind of work. Or so a Viet vet buddy of mine tells me. He also told me, though, that if the NVA or VC caught you with one, they executed you on the spot. They considered you a war criminal. I think I would have taken my chances on that one.
I’ve got three and any of the would be my go-to gun.
The real weakness in the platform is the magazines, not the gas system. I’ve never had a problem caused by propellent residue, but rather piss-poor USGI magazines and other foreign matter (sand, mostly).
I just picked up ten of the new Magpul P-Mags (practically indestructible) and my rifle functions flawlessly. When I want to practice malfunction drills, I have a set of six USGI mags that I’ve carried for over 20 years. Bent and cracked feed-lips present quite a training challenge.