For the folks that keep a loaded chamber try this little trick.
Put a piece of tape on an UNLOADED or empty shell. Put the safety on, and make sure the shotgun is ready to fire. Load the empty shell. On your carpet, let the shotgun fall over or drop it from waist level. Simulating the gun accidentally falling over or being dropped. Then inspect the piece of tape to see if it has a hole or mark where the firing pin made a strike.