Machinery Registration cartridges are made for several purposes, not only for correct weight of a “Loaded” Cartidge" but also variants Plus or Minus weights from Standard, to make sure that a functional Tolerance in the machinery can be set ( especial for “Check weigh” machines, which have a very small variance inbuilt to allow the majority of cartridges to pass through as “Correct load” yet still allowing for the normal production variation of Bullet and case weight. Over or under weight cartridges are pulled down and powder charge checked, as are the other components, and a decision taken whether the percentage of “rejects” is significant enough to “Reject” the entire Lot, or simply the reject/s are a “one off” defect, such as Two bullets in a case, or Bridged Powder (Impurity causing a reduction of Powder charge, or other defect in Powder delivery.)
QA is so strict in Military ammo production…you should see the list of reasons for rejection or re-inspecition of a Lot of Cartridges set down by Ordnance Corps.
As to the Weight of a dummy cartridge (Drill Inert) these are simply the Bullet and Empty case, with or without primer cup. These are not meant to be used for “checking machinery” but only for Drill use. and the difference of the missing Powder (and primer) Mass is immaterial to correct mechanical functioning of a Gun…