I have purely abused a number of factory .223 barrels ( Shot them hot and dirty...lots) and I would start to see some wear and groups opening at about 9,000 rounds.
Had my favorite rebarreled with a Hart Bbl, and Ive tried a lot harder to be kind to it.....its got about 8,000 on it now with no visible sign of wear....It really does seem to help if you don't shoot them really hot and really dirty... whistle
Ingwe

"...the left considers you vermin, and they'll kill you given the chance..." Bristoe