According to the late, great Gale McMillan, who should know, given his record of building winning rifles, claims that the whole barrel-break-in thing was started by a barrel vendor who intended for people to ruin their barrels so they'd buy more. He figured that, at worst (for him), the "break-in" rounds would use up some barrel life, and at best, the rifle would be overcleaned to the point that it would be damaged, and a new barrel would be necessary.
Gale's advice is to shoot your rifle, and clean it when you're done shooting.
He also went on to explain (and confirm) the insane practice of using bore paste and other abrasives in a new barrel, which removes rifling along with copper, and does so unevenly.
Of course, lots of people believe in barrel break-ins, and Gale admits that it might not be a bad idea for a cheap barrel, but that any decent barrel won't need it.
-Troy