The only test I've ever seen of "break-in" procedures compared two barrels that were as nearly identical as it was possible to make them. One was broken in by a shoot-clean-shoot procedure, the other was installed and shot with no special treatment. Afterwards, there was no difference in the accuracy of the two barrels. The conclusion was that while break-in procedures do no harm, they do no good either. I'm sorry I don't have a citation, but if I find it I'll post the reference.

Take care, Tom