We've got this criminal who likes to interrogate people via Russian Roulette.
While his captive watches, he empties an unremarkable-looking 6-chamber revolver, re-inserts a single bullet, spins the cylinder and slams it closed, then points it at the captive's face. Then he asks his questions, pulling the trigger each time he's unsatisfied by the interogatee's reply.
Because he does not re-spin the cylinder between trigger-pulls, the chances increase each time that the next chamber will hold the bullet. Thus, each successive question conveys more threat than the last. Our criminal knows this, and wants to maximize the number of questions he can ask. He also wants to give himself the option to end each interrogation without killing his captive.
So, what he think he needs is a special pistol that somehow guarantees that the cylinder will slam into position such that the bullet is in position farthest from the firing position.
What he needs:
- it should not be obvious to onlookers that this pistol is unusual in any way; ideally, it would pass casual inspection by a civilian who knows what Hollywood knows about guns
- if the pistol has a real bullet in every chamber, it must be capable of firing each like a normal pistol, because this is the same gun he uses as his regular sidearm
- he must be able to perform his prep ceremony, because it's a key part of the intimidation, and he enjoys doing it
- the pistol must really fire the bullet when it comes around -- he often does execute the captive using this weapon, and he doesn't want his goons to know the game is rigged so their own reactions don't give the game away
- must be doable for no more than $100,000 US
- setting is real-world 1990s; no magic, no aliens, no capes, no super-tech
I'm not married to the idea that the cylinder has exactly 6 cylinders.
I need to understand the details of your idea clearly enough that I can describe them in the story when it comes time to reveal to the reader how this criminal arranged this, including what kinds of tradespeople he needed to hire (and, later, murder).
Post-selection update to address a persistent topic in the comments.
Using blanks is unacceptable for an obvious reason: firing a blank makes a detonation sound that every observer will notice. Firing a blank is not indistinguishable from pulling the trigger when the chamber is empty.