Let’s see... must be a bolt action or a breach loaded weapon, loaded with too small of a cartridge, and there is no powder in the cartridge, but the firing pins is just able to hit the primer, and the resulting “pff” pushes the cartridge out the end of the barrel.
No no no... there is no rifling in that barrel so its obviously a smooth bore muzzleloader. Some idiot didn’t have any bullets so he shoved a cartridge down the barrel on top of the black powder charge.
yeah thats it.