Follow-up for all, if you care (lol):
Ammunition used in testing:
Hornady 190gr Sub-X subsonic
S&B 200gr FMJ subsonic
Halworx 200gr REX subsonic
Ammo Inc. Stelth 220gr TMC subsonic
Armscor 147gr SUPERSONIC
American Eagle 150gr SUPERSONIC
To get MY 300BO with 8.2" Rosco Mfg barrel and my youngest son's 300BO upper with 8.2" Rocso Mfg barrel to run all the ammo listed above, I had to:
1) drill gas port out using #39 machinists bit
2) H1 buffer: JPSCS-15-H1-LAW for my 300BO and a traditional H1 buffer in a separate lower that I have (my M4 which mirrors that of my youngest son).
3a) Superlative Arms AGB at 18 clicks open OR 19 clicks open for MY 300BO 8.2" barrel upper
3b) Ultradyne Quantum AGB at 8 clicks open (15 clicks is max open) for youngest son's 8.2" barrel upper
I had originally had a 10.5" Rosco Mfg barrel but to make my SBR a true "backpack" SBR, I had to build a 2nd upper with the 8.2" barrel. Originally used a JPSCS15-H2 buffer, but had issues with Hornady 190gr Sub-X never cycling the rifle.
So, when I made the 2nd upper with 8.2" barrel, I took the time to test and re-test to ensure my results made sense. I also received some sage advice from @98Z5V which helped the final steps of my testing.
The 8.2" barrel will run every type of ammunition listed like a rockstar with ejection patter anywhere from 2:45 to 3:45 depending on the projectile.