With an EMPTY gun close the cylinder, cock it and then pull the trigger to drop the hammer while continuing to hold the trigger. Look for the tip of the firing pin through the gap between the back of the cylinder and the rear wall of the frame. You may have to push forward on the hammer while holding the trigger. If it’s not an inertial-type firing pin you should be able to see the firing pin through the cylinder/frame gap. If it is an inertial firing pin you may still be able to see it momentarily flash through the gap.
That may give you an idea of what’s going on.
