There are three ways of effectively suppressing a revolver. One is to use a revolver that has no barrel-cylinder gap. There are such things but they are low power and obsolescent or obsolete. (i.e. Russian Nagant.) You can hang a can on the end of one of those and it does work. Two is to build a silencer around the whole weapon. It has been done once that I am aware of. It is very large and awkward, sort of like an oatmeal canister with a handle. The third is to use silenced ammunition. Such things do exist and are not addressed by current U. S. law. During Vietnam the army developed a special weapon-ammo combination for tunnel rats. The barrel was cut off right at the end of the frame. The ammo (reduced power .44 mag) had a buckshot loaded over what amounted to a miniature condom. The condom expands and contains the flash and sound signature of the weapon. This ammo was called .44 QSP (quiet special purpose.) A Russian outfit, UDAT, currently makes an interesting revolver which fires 32 gauge ammunition which includes, among other things, silenced rounds like this. I have only seen photos, never an actual weapon. They are not approved for import into the U. S. I have heard they are popular with armored car drivers in the old USSR as they have a wide variety of ammunition easily available, including gas, A.P., etc.
Essentially silenced revolvers are Hollywood B.S.
