First off I don’t think modern steel has anything to do with smoothbores accuracy, it’s more about barrel thickness. Modern barrels for the most part are clubs compared to most old barrels unless you lump punt guns in with the older fowling barrels. Secondly, twenty yard shot don’t mean much of anything. Where a smoothbore really shows it metal is when the velocity starts to bleed off, that’s when the ball starts to drift.
I think the most important lesson to learn if you are going to get the most out of your tradegun, or fouler, is to scrap all the knowledge you’ve accumulated from shooting your rifle, and start fresh, don’t apply any rifle shooting techniques to shooting your smoothbore. And the less wads, cards, and patches, you put into the load the better.
Hungry Horse