some very niche Special Forces stuff. Basically, in urban enviroments, you won't necessarily be dealing with super long ranges, and there's issues with concealability - if you need to deploy a rifle at a window, obviously the barrel will be poking out and give away your position. So, in certain very specific situations, it makes sense to use a revolver as an improvised sniper weapon.
The Forgotten Weapons video that Zoryn posted goes into more depth
For what purpose?
some very niche Special Forces stuff. Basically, in urban enviroments, you won't necessarily be dealing with super long ranges, and there's issues with concealability - if you need to deploy a rifle at a window, obviously the barrel will be poking out and give away your position. So, in certain very specific situations, it makes sense to use a revolver as an improvised sniper weapon.
The Forgotten Weapons video that Zoryn posted goes into more depth
Oh boy my time to shine! Forgotten Weapons has a video on this exact set up
https://www.youtube.com/watch?v=P1zEUGck8NE