Here is the easiest way I found to adjust the BHOA.
Set the BHOA assembly in the lower.
Attach the upper with the .22 BCG installed.
Turn the rifle upside down and look into the mag well. You will see the set screw adjustment at the back of the BHOA
While pulling the charging handle slowly back and forth, moving the bolt, feel for drag while slowly tightening the set screw(clockwise)
You will reach a point where the bolt will not close all the way.
Back the set screw out 1/2 turn and make sure the bolt closes when you let it go.
This has worked for me.