On the 'spent cases as projectiles' front

Who knows, if things get real dicey this may be useful to some... just watched some youtubers who found that spent .40 s&w cases were just right to be loaded into .44 mag cases and mildly propelled in those .44's acting as brass bullet jackets engraving the rifling just fine. Those spent .40's were filled (cast) with lead and their mouths were partially closed (coned) to resemble a large hollow point. At close range they did a respectable job against the usual 'reactive' soft targets... water jugs, ballistic gel, etc... and even peeled back at times like a copper jacket. Yup, thought it was interesting, these experimenters... sounds like something Jim Taylor would come up with to keep under your hat until needed.