IMO, the idea of breaking in a new barrel was invented by the barrel makers in close collaberation with the cleaning solvent/ramrod/cleaning brush boys.
The way I break in a gun is to use a patch or two to remove any oil & grease from the bore, then shoot the thing and zero it in. Then clean well when you get home. Clean it every time after shootingit to prevent rust & corrosion.
None of this other crap is necessary, and will just wear out the bore sooner.
The rifle that fired this, and many other similar, targets, was "broken in" this way. (6mm Douglas Premium grade barrel - that's FIVE shots @ 100 yards...)
I could show you MANY SIMILAR targets shot with various rifles of various calibers, all of which got no special treatment of the new barrel...
