We make rifles for shooters.
I actually have a "barrel break-in kit" that would literally have me to use up approximately half of the barrel's life breaking it in through a multi-step process using proprietary materials. The kit costs as much as the barrel.
We have a break-in procedure for those who are adamant about having to have one. It takes about a half an hour and requires thirty rounds of ammo:
First ten rounds: Single loaded, fire each and run lightly oiled patch down bore after each shot.
Second ten rounds: Load three rounds, run patch, then another three rounds, and another patch, and four more rounds, andanother patch. Always make sure that the rifle is unloaded now that you're using multiple rounds in the mag.
Third ten rounds: Load five rounds, run the patch. Another five rounds, run the patch. Again, make sure it isn't loaded/no rounds in the mag when running ther patch.
And it really isn't necessary.