first time I thought it was wrong and the rifled barrel must be for the 24/46 or the 28/46 case but booth barrels are stamped with "20" as the last pic shows. so its realy for the 20/46 and the 20/65 case and I wonder if the barrel's are made this way they use a roundball of the same diameter.its a great boregun with a much stronger action than the Husqvarna Mod. 17a anyway.wish I had a place for it in my gun safe.