Indeed it is truly amazing what you can wake-up and learn on a foggy morning in northeastern Montana...especially in a reloading forum!
I've fought this battle - and I lost! Truth is, the *CENTER OF MASS* won't move which comes to clarify that the gun itself will start moving as soon as the bullet started moving down the barrel - in order to keep the center of mass of (gun + moving bullet) in the same spot. No matter if it is revolver or semi-auto.
If you have some time, check this entertainig link (though extensive):