Jim - There is a long thread here some years ago about it, I do not know how to find it!!

I shot it under a dealer's certificate at the time (awkward laws here) but cannot remember this load

This was at 25 yards offhand - about as good as I can shoot!
10 drams BP was certainly "stout", your 12 drams would be interesting

Good luck shooting yours, I wish there was more opportunity over here

Tony