Who can't hit what they are shooting at?
The military knows the average grunt can't hit the broadside of a barn, even when inside the barn, so they want the maximum amount of lead flying through the air.
I don't believe the MILITARY believes or knows that. Maybe the Army knows that, but not the Corps.
In Fallujah, they wanted an investigation (go figure) because they thought the Corps was executing ragheads because of all the headshots. Upon completion of that investigation, they discovered that Marine grunts were making one shot kills thanks to their optics.
Now I don't know the unit you served in, but based on my own combat experience that is good shooting. Frankly can't do much better. I do assume most of those were at 100yards or less. But I figure, a single head shot on a bad guy is as good as I can expect from my troops. YMMV
Now this may be news to you, longer barrels tend to give one more accuracy and lethality down range, as compared to the shorter barrels of the same weapons. Oh yea, more reliability is a good thing too. At least in the war I was involved with.
In Afghanistan an American reporter stated that he could tell who was shooting by the number of rounds fired. Ragheads would rip a whole magazine, snuffy would fire only a couple rounds.
I know, sort of blows your whole thesis. Facts have a habit of doing that.
Weight of the basic load of ammo means a lot. It's easy to say soldiers should be tough enough to carry a whole bunch of 7.62 when dismounted, but most people haven't walked very far carrying 40 pounds of IBA, helmet, several liters of water, a couple hundred rounds of ammo, frag grenades, first aid supplies, and commo gear. Try it and see if you still want an M14 or other legacy rifle.
I don't know the distance of an average patrol in either of the sandboxes, but I can promise you in my two tours with the 3rd Mar Div in Vietnam I did a hump or two. Trust me.
My belt, Flak jacket and Helmet (the ole' piss pot) weight was at 76lbs. That included 9 of my M14's magazines that were on the belt. Then we put on our radios, a little heavier than today's models, particularly the PRC 41 (UHF) vs the PRC 25. Packs, ammo, belt for the gun, bandoleer for the blooper, etc.... If you had mortar's attached we carried some of them too.
Our battle loads could easily get to 125+ pounds depending on the mission and type of supporting arms attached. And still folks wanted their M14's. I did. For us it was, "IF it would keep your alive, take it."
Let me tell you my friend, everyone was trying to buy, trade, or steal my M14 after we switched to 22's. Why? Fewer rounds in a reliable rifle is better than more in one that is not. I could shoot through a lot of cover. The M16's could not.
I started rifle shooting competitively in the middle 50's in the NRA's junior programs with the 22. The Marine Corps taught me how to shoot out to 600yds with Iron sights on my M14 and M1 Garand (carried that in ITR). It is easy to hit a guy out at 300 + yards. Part of it was a different era. Many of the troops, like myself, were shooters before we go to the Corps.
Maybe you can't do it. But the better shots, not snipers expert riflemen grunts in my day, with M1 Garands and M14's could hit with reasonable reliability at range. AS AT&T used to say. When we needed to we could "reach out and touch someone."
The M14 had a big advantage over the Matty Mattel. It tended to keep ole' snuffy alive. I never had to bag and tag a Marine because his M14 failed. I have bagged and tagged several who's M16's did.
I only used my selector a few times, and not very effectively. Semi auto is just fine. Besides if you're in a position that has to go to final protective fire, semi Auto is damn near automatic, and a lot more accurate. One other advantage, when you get over run, or you over run the enemy, the M14 makes a much better baseball bat.
Go figure.
Fred