I've shot out a couple of barrels, and the issues are visible and easy to spot (fire-cracking, worn grooves, chamber bloat, inaccuracy, round-count, etc.). My hypothetical for you gurus out there is ... can you ever burn through an action to the point where re-barreling won't help, and if so ... what are the visible symptoms of a shot out action in a bolt action rifle? Not there personally, but a buddy asked me that question as he watched me mount a new barrel, and I honestly didn't know the answer.