In one frame, if you look closely, you'll see that the "nipples" appear to have a hex configuration and suprise suprise, just happen to fit a top hat musket cap!? I think these good old boys bought a pig in a poke, as the Rev. Forsythe did not invent the concept of the percussion cap until the early 1800's. All early period prints and etching displaying such "gonnes" showed the use of a slow match.
Rick