In the days before antibiotics, and bathing was not often done think about all the dirt, grit, bacteria, that would get carried into a wound by the bullet.
The .41 Rimfire derringer was such a gun. It was so low powered, it’s main form of killing was the infection caused by it.
During the civil war it was the mark of a good commander if he tried to make sure his soldiers put on clean under clothes before a battle. The idea of infection was dimly understood, but the connection between unclean clothes and infection was understood by the better educated commanders.
CC