PONY: Lead takes about five strikes to seat the flint into the lead wrap. There are subtle curves and waves in what appears to be a flat surface of the flint, and those waves have to marry to the lead. I fire the gun five times, and then use my turnscrew on the cockscrew to tight the screw down one more time. I often get up to a 1/4 turn of the screw, no matter how tight I screwed the thing down the first time. I use a thin hammered sheet of lead I get from hammering out a round ball to wrap the flint, because it grabs the flint better, than any leather wrap I have ever used, unless I glue the leather to the flint. It also does not give when the flint strikes the frizzen, becoming a shock absorber, when I want all that energy to cut steel out of the face of the frizzen, and throw it into the pan as hot sparks. I get more sparks, and they are hotter( whte hot compared to dull red/orange in color) than I do using the same flint wrapped in flint.
I did not believe this was possible, until a friend took me to his workroom one night, turned out the lights in the room, made me wait ten minutes for my eyes to adjust to the dark, and then tried a flint with both leather and lead and let me decide for myself which gave better sparks, and which prevented steel bits from loading up the edge of the flint. I tried it with his flints at his place, and then tried it again at my own home with my flints. Later I let my brother see the " test " at my home, and he then went back to his home and tried the test with his gun and flints. Half a dozen other folks have tried the test, and all report that the lead wrap works better for them, too.
If you like leather, stick with it. If you lose a flint because the leather just won't let you compress it hard enough to hold the flint in your jaws firmly enough, then switch to lead.
You can always do the test. But, be fair to the flint, and your own eyes. Give your eyes the time to adjust to the darkness, before doing the test. Its very difficult to see the color differences in the sparks with any kind of light on , or when your pupils are constricted. Its also difficult to see the difference in quantity of sparks if your eyes are not adjusted to the dark, and fully dilated.