1st: HCI wants to ban ALL handguns, and to a lesser extent, all guns. I am sure that blackpoweder pistols come under 'all", but also that they are hardly a prioity target currently.
Kinoons; A black-powder rifle is a lot more powerful than a pistol. However, even a modern high-powered rifle, or a magnum pistol will not “knock someone down”. I have seen films of large powerful rounds fired into a hanging animal carcass, and they hardly move. However, the pain, force & concussion can cause you to collapse.
I know several folks who have been hit by modern rounds while wearing vests- and it is “like getting hit by a (hardball) fastball”. Now, if a pitcher hit you in the stomach with a fastball- that would not “knock” you down, but it could well make you double up with pain, the wind knocked out of you, and you collapse.