It's awfully hard to do this remotely, but it sound likethe couple of 'shatters' end up shortening the flint just enough so it travels further forward in the hammer's arc before it hits the frizzen, which causes it to strike the frizzen lower and at a dowward shaving angle...no more shatters and lots of sparks...you just want to achieve that same thing with a new flint from the git go...don't want it shattering when you drop the hammer on a 10 pointer