Thanks Craig for the info!
It is very intersting.
Im not an expert nor a gunmaker I have only made a few muzzleloadiers and I proof some of them.
Many years ago I made a 12 bore smoothbore rifle to be shot with double charge as hunters in Ceylon according to Baker. To proof it I shot the provitional beligium or british proof (IIRC) that is double powder charge with 1.33 lead (I used 7# shot).
I also made a 12 bore howdah pistol and also proof it the same way.
Both guns were underhammers.
Thank you very much.
Martin