I believe the 5.56 is designed to tumble on impact.
Depends on shooter to target distance.
The 5.56 mm round has to slow down a little before its legendary tumbling effect begins to occur when striking a solid target. Before that, the round is still stable from barrel rifling and still too hot (fast); it simply punches neat little holes in the enemy.
This lack of desired effect was being observed during close-in combat (100 yards or less) in Iraq and Afghanistan. It is reported to be the rationale being used by the Army and Marine Corps for looking at returning to larger calibers (6.8 and 7.62 mm) for the next generation infantry rifle. I’ve read (somewhere) that 6.8 mm mm is considered the minimum diameter for a bullet to check the boxes for accuracy and lethality over its entire range while minimizing ammo and weapon system weight.
At this point, the conversation goes sideways into specific weapons, intended roles, users and their training, tactics, mobility, present and future battlefields, etc., etc. So you end up with modern infantry that look like action figures from a SciFi movie and the terms “dumb” and “grunt” are now considered mutually exclusive.