I have the same Brooke Barrel.
They are strong as hell.
I don't know what max safe load behind a 1" lead ball is in this barrel, but what I do know is that the recoil from every load mentioned here so far would be tremendous.
I have been using 1F in it behind lead balls. Think much less, at least to start with, until you see what you are up against for recoil.
Start at 50 grains and work up. I suspect that around 100 grains you will want to evaluate your needs against what is happening to the gun carriage.
For blanks, well, PM me, or Caz, or Tropico, or ask Michael himself. We all discussed our loads amongst ourselves and with Michael. None of us really wanted to post the blank loads in public, as loading procedures for blanks for smaller guns tend to disagree with the established norm for the bigger ones and we did not want to create controversy.
Michael did some attempted destructive testing and we were all way under that, yet for blanks we were making way more noise than a 12 g shotgun every could.