There is more pressure per square inch applied with a small object than a large object.
Actually an angle hit from the front edge of a semi-auto handgun will break a window in a car/truck very efficiently. Don't ask how I know, but it works. I would guess the same would be true of a revolver or any piece of steel, including a tire iron.
Just make sure your finger is not on the trigger.
Again, has to be on an angle, allowing for a smaller area to contact the glass.