just a note: Be careful about using a bullet, even a spent one, in that breach. Most Cons have a rule of "No Live Steel", which means "No steel that looks like it could kill." some also have a rule of "No bullets or explosives, live or otherwise", which means if it looks like it has a live bullet in it, it's not allowed. Maybe paint the bullet blue (The universal color of training [TTR] Rounds).
Oh, and if that bullet was just for scale? you should totally make the breach spring-loaded with the bullet behind it. It'd be epic.