Do any of you guys belong to the NMLRA? This month's magazine has an article on a flintlock in-line from the mid-1700's. I think it was German or eastern European. In any event pretty cool. A small flint was put on what would be the firing pin on a modern in-line. There was a trap door on top of the barrel behind the breech plug. The back side of the trap door was angled at 45 degrees and was the frizzen. In other words as the flint drove forward it hit the sloped trap door and pushed it up as it scraped against the steel and created sparks. At the back of the plug was a dished area to hold the priming powder- which was exposed when the trap door flipped up- firing the gun.
Pretty cool. Why didn't it replace the regular flintlock? Well the mechanism was superior but the maintenance was the problem- impossible to clean and bits of broken off flint could jam up the works.
The firing pin had a rod/bolt- just like some modern in-lines, that was pulled back to cock the piece.