Blue-painted Tartar missile Guided Missile Training Round on a Mk 13 naval launcherMilitary rifle drill round with fluted, perforated, and tin-plated case to distinguish it from a live cartridge.
A dummy round or drill round is a round that is completely inert, i.e., contains no primer, propellant, or explosive charge (filling).[1] It is used to check weapon function, and for crew training.[2] Dummy ammunition is distinct from "practice" ammunition, which may contain smaller than normal amounts of propellant and/or explosive.[3] For example, the M69 practice hand grenade[4] 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.
Media related to Dummy cartridges at Wikimedia Commons 
