Why cannot pull the trigger if there’s no bullet?

There is no written rule dictating that the actor should check it.
Of course the armorer is charged, that’s his responsibility.

Should a pilot assume that his fighter jet is ready, really ready, when he’s told it’s ready?

If a pilot experienced a crash due to a premature explosion of the carried bomb, should the pilot be responsible? What if the landing gear failed? That’s not even the same case. Why the heck a real gun is used if there is no need to have a bullet and pull the trigger? Why does the gun need a trigger? Were other producers charged for an incident like this happened before?