Can a gun accidental discharge buy hitting the hammer if manually decocked by riding the hammer forward while pulling the triiger so the hammer doesn't hit the primer on the bullet very hard?

Answer 1

Yes, it sure can. Keep in mind that the blow from the hammer has to be substantially heavier than what's actually required to ignite the primer. Doing so helps ensure you won't have a misfire due to the primer not being crushed properly, so a lighter blow than what the hammer normally delivers can still set it off. That being said, modern ammunition is pretty robust, and most modern firearms have mechanical means to avoid what most people see as the main concern with exposed hammers, that is, ignition from either striking the hammer, or the gun being dropped and landing on the hammer. Revolvers can have a transfer bar to isolate the hammer from the firing pin, such as used by Ruger. Smith and Wesson uses a rebounding hammer, which raises the hammer back up as the trigger's being released. Keep in mind that these two devices are more to address the concern of the hammer being struck as it lays on a live primer, rather than the specific case you brought up. Most self-loaders (semi-autos) have a floating firing pin, which, technically, is too short to transfer the force from the hammer directly to the primer. It works through inertia. The firing pin is lightly spring loaded against the rear of the slide. As the hammer is dropped by the trigger sear, it's forward momentum stricks the firing pin with enough force that it actaully overtravels, striking the primer. It's the same principle as using the cue ball of a pool table to send another ball into a pocket. This style probably has the greatest resistance to the issue you brought up.