I've had some test runs by dry firing (pulling the trigger without any ammo) my shotgun with the barrel in my mouth a few times in the past. I've somehow learned roughly about how much pressure (in lbs) that I need to exert with my finger in order for the gun to go off. When I hear a click, then it means that had there been a live round in the chamber, the gun would have gone off.
As of now, since I'm not actively suicidal, I don't really think of offing myself. I'm just passively suicidal, daydreaming of suicide from time to time.