After the shootout in the bar, the 'accountant' comes out. You can see very clearly that his gun is equipped with a silencer, but when he uses it to shoot the bartender it actually makes a loud noise.
Another part about the silencer, How can you put a SILENCER on a Revolver Pistol. The gas from the discharge escapes between the cylinder and the barrel. Making the revolver impossible to silence. Check it out.
Actually, the suppressor can be attached to a revolver. In 1972 Dan Wesson manufactured a revolver that was suppressed. It was to be used by Uganda nationals to eliminate there head of state. A present from the CIA. The way it works is the space between the cylinder and the cylinder to eliminate the space. The revolver in the movie COULD be a descendent. It seems to be the same design.