I break in my rifle barrels. But not the same way and not for the reason they will be more accurate.
If it is a high end barrel, it pry was made with high end equipment and with SHRARP tools, reducing the marks in the barrel, it was also pry lapped and cleaned, so this barrel is pry good to just go shoot. In cheaper barrels, I have found that the marks dont really cause poor accuracy as they do fouling, A realy fouled dirty barrel will lose acuracy.
On a new barrel, Ill clean it before it goes out to the range for the first time, Ill shoot 1 round, and then clean to see how much copper has built up. If it seems like alot or more then normal, ill shoot 1 and clean 3 or 4 times. Then ill shoot 2 and clean 2 or 3 times and then thats it. Normaly after 10-12 rounds its not getting much copper build up in it. Most damage to barrels is caused by over cleaning it the wrong way.