Hi! I spent a lot of time to find something while I was playing dangerous waters. I recommend you ask on DW forum too. The best document so far was
https://www.globalsecurity.org/milit...14308_ch10.pdf
As far as I know, the BRC allows to calculate range based on bearing rate and speed across the line of sight. To calculate speed across the LOS you should add both your and your target speed component using sine on the innermost disk, knowing target bearing and angle on bow. If I remember well, 1 degree of bearing rate at 1 mile (2000 yards) and aob 90 means the speed across the LOS is 1 knot.
Edit: remember, for historrical accuracy, that BRC was introduced during Cold War.