Indeed, some ARs are different than others. I still find the loss of accuracy in the ARs firing bimetal bullets convincing. The result that the AR using Federal copper clad bullets was still accurate at 10K rounds is proof. Both Wolf and Brown Bear barrels needed replacement around 5K rounds.
That being said, AR barrels are relatively inexpensive at present so the trade off is just this: shoot cheap bimetal bullet ammo and replace the barrel with the money saved by not buying brass cased copper clad bullet ammo.