What rules were used?
My own and under development but not for publishing. They are designed for very fast play and large groups.
I do not hand them out as a set but give a quick description (one minute) of what each player needs to know (move rates, weaponry, player and NP characteristics etc). Most of this stuff is made available on the table.
With large groups, I try to get them to self-referee. If you're going to cheat while playing with toy cowboys, there's probably no hope for you.
The tools and mechanics are so simple that, after the intro, it becomes a test of character.
We had one player who climbed onto a roof and started calmly picking off civilians with a rifle. Another decided on a whim to rob the bank, a turn before the real bank robbers turned up. A third forgot the basic physics of throwing sticks of dynamite.
Rusty horseshoes are awarded to the best actions and decisions of the day and aren't about "winning".