Hmmm... we do not have much of western locations (or western-themed stuff for that matter) around here. But it has just the right mood of a dirty dusty small town, where rough men hang around, and all wait for the better day.
I love it as an item, I really do, but I don't think it is playable.
Think about it: If it never works, who would try to use in extremis? (OK, maybe it is only my players that forget everything in their packs when under duress...) Conversely, if anybody did try it in the appropriate circumstances and thus figured out how it worked and described its unique power, then it would never work for anyone who heard the description - and it's certainly the kind of story that would get around!
I like it a lot, almost enough to bump it up a grade. I'm not into guns in my games, but thats just preference. If I were to use it I reckon it would be an NPC, because as pointed out, most players wouldnt use a nonworking gun in dire conditions.