I only ask because I'm incredulous that Armbrust loads made custom to that gun would behave in such a drastically awful way.
The Armbrust load is a duplicate of the Westley Richards Fauneta 20 bore loading and Huvius is aware of that. The load duplicates 1500fps and a 425gr bullet. There were however one or two lesser loadings used by Holland and Holland in the 20 bore Paradox. There may be perhaps other period loadings for the 20 bore ball and shot. Rifled choke guns are rare and extremely rare in the 20. Probably just a few hundred made by all makers. Downloading this cartridge shouldn't be a problem. The Armbrust load getting the velocity at the appropriate pressure was genius.
