Does the rifle fire consistently? My locks do not produce a "shower of sparks" but they *almost* always go bang when I pull the trigger.

You can also use lead to hold your flints. I find lead holds a flint more rigidly than leather and therefore you get more sparks.

To use lead: flatten a round ball using a mallet or hammer. You want to pound the lead thin enough so you can wrap it around the flint with enough lead for the jaws of the c0ck to sink into. Trim off excess lead and be sure to check the travel of the c0ck you do not want lead scraping against your stock or barrel. When tightening the jaws perform an initial tighten. Wait a while and then tighten again: lead being a soft metal will conform its shape to the shape of the flint and sink into the grooves of the jaws.

And like BPS said don't bother with the manufactured flints the Black English flints work great.