Our old systems (the ones us old guys used/trained on like the M14) had iron sights w/ 7-MOA front sight blades on them. We trained on and were expected to hit pop-up targets at 300-350 yards during qualifications -which we generally did -although with varying degrees of success.
When we did fail from the rifle pits, the failures in those days centered around:
1. Targets were hard to discern (or even pick up from first emergence) as they appeared at those ranges
2. That 7-MOA sight blade spanned 25 inches at 350 yards, grossly over-shadowing the silhouette target's width at that range
3. We were battle-zero'd to where we had to hold at the top of that 350 yard silhouette -and thereby lost completely it as often as not because of 1 & 2 above
4. Range guestimates were just that, with little/absolutely zero ability to adjust sights to compensate during qualifications (or most flare-up firefights for that matter).
The introduction of the M16 (in my time) didn't change any of that. But no one really noticed because engagements tended to be shorter-range anyway, and everyone was too busy complaining that M16's reliability totally sucked.
We fixed the black rifle's reliability through a combination of weapon design, individual maintenance equipment, preventive maintenance, and training to the point of cartoons with sexy broads doing the instructing. But we never had to really address the effective range issue because, ... (well), it was never an issue... until now.
Things change. Now range ~ an issue --and we have band-aidecl/jury-rigged any number of things to try and make the issue go away -including some very good things like ACOGs w/ 4x magnification, finer sighting reticules, and auto-rangefinder/ballistic drop compensators. But is has left us with a basic problem we didn't have with the 30 calibers: effective terminal ballistics at range.
We've got the rifles that now function reliably, are relatively lightweight & compact, and are imminently controllable in a firefight --AND the no-brainer optics that will double their effective range for the average infantryman -whatever that effective range
was in my time and after.
We just need to finish up the solution process with a matching cartridge that takes advantage of everything else we've done, and for as little change in possible to weapon system (including receiver) design, weight, dimensions and effect on the shooter.
We owe it to the shooters after now a half century.
Has the US ever lost a major battle because the 5.56mm was not as good as some other cartridge? Answer No
You sir are 100% correct. Even times where weather prevented Air Support and it was Rifleman against Rifleman, the American soldier prevailed.
"L'audace, l'audace, toujours l'audace!"
And with that, I am so reminded of this bitter exchange 37 years ago:
"You know, you never defeated us on the battlefield," said Harry Summers. To which Colonel Tu replied in a phrase that perfectly captured American misunderstanding, "That may be so, but it is also irrelevant."
I have to ask myself, how many body bags have we brought home -- even though we "[n]ever lost a major battle because the 5.56mm was not as good as some other cartridge..."?
Only an answer from the Ops Analyst would take the tact that cartridge change "...wouldn't have been worth the money."
