Dry firing a hammerless double-barrel shotgun or a revolver without snap caps or other protective measures can indeed lead to damage, especially to the firing pin or other internal components. In the case of hammer-mounted firing pins, the firing pin can hit a stopping plate or continue forward, causing damage to the firing pin itself or other parts of the firearm.
Using snap caps designed specifically for the type of firearm you have is highly recommended when practicing dry firing, especially with firearms that have hammer-mounted firing pins like revolvers or older double-barrel shotguns. Snap caps provide a cushioning effect that helps prevent the firing pin from striking against hard surfaces and causing wear or damage.
