Now, on to the subject of revolvers and cylinder gap...
"As for suppressing a revolver, it might make a little bit of a difference in the overall sound, but probably not much; too much gas escapes from the cylinder/barrel gap."
In general, the above statement is true.
I HAVE fired revolvers with suppressors attached and which have not had a regulated cylinder gap.
While the report was certainly lessened, it was by NO means silent. Firing a .357 so equipped was NOT a good idea without hearing protection even though the gases exiting the muzzle were controlled.
I would describe the sound of the gas escaping the cylinder gap to be about as loud as a .22 LR or a .22 Magnum out of a pistol.
The reason the Russian Nagant revolver worked with a suppressor is because of the rather unique gas seal system in which the cylinder cammed forward and the mouth of the cartridge entered the forcing cone on the barrel.
This is a picture of a Nagant cartridge (free use from Wikipedia):
The bullet is fully enclosed below the neck crimp. On firing, the crimped brass expands and seals the cylinder gap. No gas escapes from the cylinder gap during firing.
This is a picture of a Bramit device, a Russian/Soviet designed suppressor for the Nagant revolver.
It was not the only design to be successfully used on the Nagant.