That's not a revolver. It looks more like a Weldey or an Automag.
The way the breech area widens instantly rather than gradually made it look like a revolver cylinder, though I could see it being a poorly drawn Automag, especially with the wide frame under the barrel. I may also have been biased since Japanese police (that Fletcher is dressed as) use S&W revolvers, though taking a better look, those are clearly different.
