All my Flintlocks are TC Hawkens, same lock as the TC Firestorm.

Agate flints are expensive, almost impossible to sharpen, and don't last very long...I've tried TC's regular, TC's premium, Arkansas agate flints, etc, then tried some black english flints and threw the agates away.

I shoot every Saturday and average 40-60 shots per flint in my TC Hawkens...using the same flint for an entire 40 shot range session...either lightly knapping it or flipping it over about every 10 shots to keep 100% reliable ignition.

October Country has the best price for Tom Fuller black english flints...you order the size flint by wide of the frizzen face, for TC locks, 3/4" black english flints are outstanding.
Bulk bags of 25/50/100 3/4" flints from October Country cost approximately .75 cents each...speak to John or Linda, tell them a guy from North Carolina recommended them