A dummy round or drill round is a round that is completely inert, i.e., contains no primer, propellant, or explosive charge (filling). It is used to check weapon function and for crew training.M922/M922A1 40mm Dummy Rounds (fas.org) Dummy ammunition is distinct from "practice" ammunition, which may contain smaller than normal amounts of propellant and/or explosive.https://patents.google.com/patent/US4867065A/en?inventor=H+KaltmannM781 40mm Practice round (fas.org) For example, the M69 practice hand grenadeM69 practice hand grenade (fas.org) emits a loud pop and a puff of white smoke.
A dummy is not to be confused with a blank, a cartridge for a firearm that contains propellant and a primer but no bullet or shot; a dummy does not produce an explosive sound like a blank does.
See also Dud Snap cap
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