Exploding cows, baby killers and death rays (2016)
natlib.govt.nz
natlib.govt.nz
Not because I know he invented it, or anything of the like. More that a paperclip & upside-down comb taped to the inside of a hat was a trick we used in media.
Apparently it got patented in the US [0]... Which probably means the patent is still valid. (Incidentally, going through those that reference it, you can see patent-files' transition from mostly-technical to mostly-legal.)
As I recall, the successful bullet was filled with phosphorus and had a small hole that was re-opened as it ran down the barrel when fired. Thus it spewed flame along its whole flight and as it penetrated the Zeppelin hull where hydrogen and oxygen where a good ratio.
But as I can find no citation, I must take my own memory with a grain of salt.