. . . I'm more interested in IDPA but the IDPA rule book makes no mention of dry firing your weapon to prove it's not loaded. My expereince in the world of competive shooting is limited. I could be wrong on the IDPA . . .
You are wrong. When you have completed an IDPA stage the command sequence is "If Finished Unload and Show Clear; If Clear, Slide Forward or Close Cylinder; Pull the Trigger; Holster."
That command, "Pull the Trigger," differs differs from the USPSA "Hammer Down." The point is to make it absolutely clear. Here's how it is spelled out in the IDPA Rulebook.
2.12.3.11 Pull the TriggerThe shooter will point the firearm at a safe berm and pull the trigger to further verify that the chamber is clear. If the firearm fires, the shooter will be Disqualified from the match. This requirement also applies to firearms with a de-cocker or magazine disconnect. For firearms with a magazine disconnect, an empty magazine, or dummy magazine must be inserted before the trigger is pulled, and then removed again. This command is not needed for revolvers.