The entire concept of competitive gunslinging makes me think of Harlan Ellison's short story set in a world where ranked automotive combat exists on the highways and how a middle-aged couple manages to opt-in and duel with an aggressive driver, working their way up the charts I guess.

Which I still think you would write an amazing radio play of, assuming the rights issues are not an inherent hell.

Annoy the wrong gunslinger and you suddenly got a number on your back.

I believe this culture is considered to have existed more in dime novels than the actual nineteenth century, but makes for such good fiction.