In der Praxis ist das Ziel solcher Überwachung doch dann Drogendealer und Umweltaktivisten.

I looked up the rules. According to my understanding, here is roughly what happens in a pistol duel:

There are three checks, quite similar to D&D. Who goes first (initiative), hit determination, and wounds. I can see the shared heritage.

For each of these, you have a base number from your stats. Then various modifiers are applied depending on range, movement of shooter, movement of target, wounds, weapon type, and more (e.g. hipshooting is +5 for first shot but -10 for hitting). Collecting and adding all the modifiers is what makes it complicated.

Initiative does not require a roll. Hit determination takes one percentage die roll (d100). The wound takes two d100. Example from the rules: “A first roll of 49 would indicate a wound in the left shoulder, and a second roll of 72 would mean that the wound there was a serious one.” A serious wound means -7 to your strength attribute and shows up in later bonus calculations.

Such a serious wound will take seven weeks to heal assuming proper medical treatment.

Fun fact: The rules contain more than five pages of stats for historical figures like Billy the Kid. :)

Wow, awesome story!

It seems the GM brought a lot to the setting (“I already knew quite a bit about [Tombstone, Arizona]”), so most people would not be able to create such an experience with just the game document.