I confess to being a comparative duffer with the AR-15 format. My first experience was as an enlistee with the “Mattie Mattel” XM16E2 about 35 years ago and no more real contact until the turn of the current century. No, I’m not a real expert, but I know some real experts.
The carbine isn’t supposed to be a precision rifle. I’ve used some that could nearly meet that need. The fact is, if the 5.56mm carbine (16-inch barrel or less) shoots into 2 inches at 100 yards from the bench, it will probably do everything it needs to do.
I’ve run across a few that were scary accurate with the right optics
on board. Premium ammo helps, but that’s always been pricey. For patrol use, it’s decent ammo, good maintenance habits, a sling, combat optics with backup irons and a white light are what’s needed.