It sort of sounds like The Duelists with a Predator dicking around. Overall I'm just not sure you could hang a whole movie around that pistol.
Now, it's been a while
since I've seen this movie, but I think that if it was done more in the fashion of The Red Violin it could stand a chance. I know, completely different - but I could see a movie about the pistol itself working out in that way, of course with Predators taking the place of general misfortune and sadness like in the movie