I saw a video somewhere. The anvils fortuitously have a hollow on their undersides in which the shooters pack powder, and have pre-drilled a hole in which they insert a fuse, upend it onto ANOTHER anvil, and ignite.
Well, one thing’s reassuring. Even if they outlaw all guns and all gunpowder, we can always make black powder from sulfur, salt peter and charcoal or coal (I forget which), and it packs one hell of a wallop. Can even send an anvil skyward.