The reason I altered that rule to my version, is one negligent discharge and three 'surprises': "Wait what? I'm SURE I unloaded that."
The surprises never ended up going ND, but I opened the action, and there Mr. Brass Cartridge was... that SCAMP, that PLAYFUL LOVABLE TRICKSTER!
Steel rounds are the worst about hiding in the chamber of a black firearm.
Bucket of sand around is a good idea.