I have been interested in developing acceptance criteria to determine if my 300 Winchester Magnum with a BOSS was tuned. I have asked for input from three forums. To date, 12 BAR owners have reported group size with their BAR rifle. Seven owners had a BAR with a BOSS reported a group size of less than or equal to 1".
Therefore, a BAR with BOSS rifle is tuned when the group size is about 1" or maybe a little bit better. Additional tuning of the BOSS or ammunition adjustment will probably not result in better precision giving the data to date.