From what I understand, the shallow micro-groove can't purchase the faster bullets, so the bullet goes straight across the lands until it finally starts to spin. The bullet(s) gradually wear the lands smooth starting at the breach. I don't know much about the 322, but my neighbor has a 455 that he had rebarreled. It killed the collector value, but it is an amazing rifle-smooth, accurate, rare, and it's a marlin! His is a 30/06 that was his fathers. He swears it has less than 300 rounds down the original barrel.