short barrel ARs are still accurate

The m4 loses 200 meters off it's effective range compared to the m16. Afghanistan average engagement ranges were 800m, and the m4's effective range is 300m. You are full of fuddlore, velocity is hugely important for long range accuracy.

You're claiming some obscure .276 is proof that .223 is comparable to heavier rounds because of a long range lethality test of a much heavier and faster round. That's retarded. That round had weight comparable to a .308, and a smaller diameter. The inch caliber is not a measurement of mass or velocity, just bullet diameter.

5.56 does a lot of not killing what you shoot at. One round of buckshot to the gut or a hollow point slug if not stopped by armor, is a threat ending shot. One .308 or 30-06 to the torso is a threat ending shot. 5.56 does not provide enough shock to do that, and relies on vital hits for quick stops or multiple shots in quick succession, which most civs will not manage. Fragmentation is also significantly worse than expansion - hollow points are much better against unarmored targets. Tumbling is completely negligible in consideration. And no, the military wouldn't pursue either - because the military is actually concerned with armor penetration. They want rifle rounds going through kevlar or other armor materials, not fragmenting or tumbling. 5.56 is operationally garbage for civilian use because it's primary strength is controllability in rapid fire for suppression. Suppression is a tactic that is both useless without a group, and usually illegal. It's only other use for civilians is the negligible recoil, so weak people can shoot it. There are much better self defense rounds for close range, and much better rifle calibers for medium-long.

And tumbling doesn't make it stop in drywall either. 5.56 will punch through walls fine. Tumbling is nonsense. Go actually look at ballistics gel tests of the modern 5.56 rounds.