I attended a LR Precision Rifle class this year here in Alaska With Frank Gali (Owner of Snipers Hide website) & Marc Taylor from here in Alaska. They were a Marine Scout Sniper team & now do classes together. Both say no formal break in. Clean it before you shoot it. Clan it at the end of the first range session. Don't clean it again until you see accuracy degradation or are putting it away for extended times (Months). With the 308 on many rifles Frank said his only barrel cleaning is a few pulls with a dry bore snake at 500-700 rds.
Vance in AK.
"But seek first the kingdom of God and His righteousness, and all these things shall be added to you."