There are bad ideas and then there are horrible ideas.
How about shooting a .50 BMG cartridge from a flare gun?
See what happens when a .50 BMG cartridge is fired from a plastic flare gun.
Just because something kind of fits does not make it a good reason to shoot it.
Well how about pairing up a plastic flare gun, you know the ones in boat emergency kits, with a .50 BMG cartridge? Yes it will fit and with some tinkering YouTuber Edwin Sarkissian got one to actually fire. Yes the flare gun essentially turned to dust while held in a vice.