Very neat find, WTG!!!
My father had a small connon when I was a kid that actually worked (fired)... You would fill, well maybe not fill, but put sulfur in the barrel and I believe the one he had had a similar device on the end, spring loaded, and you would place a cap inside, pull a plunger back and let it go to fire it...
Continued Good luck, & Happy hunting~
Ooop's,,, Very neat lighter too...