I have easily put 3000 rounds through my AR15 and Glock 27 and neither have any barrel wear at all.
I find this quite suprising.
Depends on how you measure it. I used it at 200 - 300 yd as a varmit gun. It just didn't group as tight after a while. I attributed this to barrel wear. I've has some other guns that required replacement parts in time too. a 1916 shotgun doesn't feed properly, and as you can imagine, there aren't any handy replacement parts. The most irritating was a colt python where the hammer spur broke. I wrote to colt saying that should be a warranty repair, but since I had it more than a year they told me TS
A .220 Swift bullet leaves the muzzle at about 4200 fps. In still air, you can see a trail of blue smoke from the vaporizing copper jacket!
At such a speed, the tiny wobble of the bullet as it leaves the muzzle is enough to wear the muzzle out very quickly. The cure is to have the muzzle re-crowned periodically.
My father and I used to hunt woodchucks in the Catskills with an old gun-collector named Abe Levine almost 50 years ago. Abe could read the wind and mirage like nobody else I ever saw. He took a woodchuck at 600 paces with that old Swift.
Whenever the gun started to lose a little accuracy, Abe would trim the barrel a little and it was good as new.
The .223 round doesn't burn nearly as hot, and unless you are fortunate to have a full-auto rifle (which also gets hot enough to burn steel) your AR should have a much longer barrel life.