The Joint Service Weapons Board-Integrated Product Team said it themselves in 2006.
The best performing systems emphasizing tissue damage, on the average, in this study were of larger caliber than 5.56 mm.
(After all of their study and analysis, they came to the same conclusions as previous teams had in 1952, 1958, 1963, 1968, 1993, and later.)
I do wonder why the focus on the .223's performance (and lack of) at long range. No, its not great at 5,6,7,8, 900 yards and beyond. It wasn't made to be. Why is this even brought up??
Because that is what I have been watching.
It wasn't meant to be a treatise on the overall effectiveness of the cartridge, just a point of observation prompted by my recent interests, with some relevance to the subject.
But, I'll lightly touch the point real quick:
Long range engagements seem to have been uncommon in Iraq - with some studies suggesting 20-30 meters being average. (From what I saw [2002-2007], I believe it.)
It was, however, a major issue in Afghanistan, where 50% or more of the engagements were 300+ meters. That is why there was a sudden, urgent need to return a bunch of M14s (and M21s and M25s) to DMR roles in the early years of the GWOT. (Again, I was there [2002-2004]. Close quarters engagements were rare outside of villages, and I don't think I was ever shot at from
less than 700 yards.)
From an analysis published in 2016 (J. A. Wesolowski):
(...) enemy combatants appear to have discovered a “zone” of operation that is within the maximum effective range of their 7.62 mm weapons but outside the maximum effectiveness of the US’s 5.56 mm weapons (Ehrhart, 2009).
The enemy combatants then implemented doctrine to stay outside of the effective range of the 5.56 mm M4 whilst remaining inside the capabilities range of their own weapons, namely rifles of caliber 7.62x39 mm and 7.62x54 mm.
Actual ranges are not mentioned specifically in reference to the above, but are discussed earlier in the analysis and inferred to be approximately 400-900 meters.
Any cartridge relies upon BULLET PLACEMENT on target.
And a bigger bullet makes a bigger hole in that place on the target.
In fairness, the JSWB-IPT report does say the same thing: Bullet placement is more critical than any other factor, for taking an enemy out of the fight (not requiring lethality).
Now, if we weren't using FMJs, my opinion would be a little different. But as long as the US military is sticking with FMJs as the standard bullet type, I consider 5.56x45 to be inappropriate.
Need bigger boolit.