9mm dummy round/snap-cap (fully rimless)

This is a 9x19mm Luger/Parabellum cartridge that has had the rim removed from it, so that it can be inserted into a 9mm chamber and used for dry-fire, preventing a real round from accidentally being loaded as well as preventing the extractor from pulling it out whenever you cycle it. When you finally want to get it out, either grab its rear end with tweezers or pliers and pull, or push a pen down the barrel to knock it out. Or maybe scream at it until you break its will and it falls out on its own. You're smart; do whatever works best.

Note that, since it is as long as a normal 9x19mm cartridge, your firing pin will hit it - it is intended to be printed in a flexible filament, not a hard one. If you cannot print flexibles, one of several alternatives is to print using several shells/walls (3 to 5 or so..?) but NO/0% infill and NO base layers, so that (based on your slicer settings) there is an open "tube" down the middle of the model that the firing pin can poke into without hitting any plastic.