I have two guns with this lock and they are both very fast, giving quick and reliable ignition. I'm sure they have each seen several thousand shots too. Usually, the groove that gets cut into the frizzen's face is only hard on flints - it doesn't interfere with ignition. But you certainly could grind a new face onto the frizzen by removing it from the lock, and holding it against a 6" bench grinder's stone. keep your thumb on the back, and when it gets uncomfortably hot, quench it in cold water, and go again. It takes a little while, but you'll have a brand new face that should spark like a cutting torch.
With these two locks on my guns, I have found that the flint bevel up gives noticeably faster ignition that bevel down. The flint strikes lower on the frizzen this way, and likely produces fewer sparks, but they are directed straight into the pan,whereas with the bevel down, a lot of the sparks shoot forward of the pan. There's nothing like a brand new sharp flint or a freshly knapped one, set as far out toward the closed frizzen face as possible.
This should probably be moved to BP Shooting Forum.