Years ago I bought a pile of parts from boxes at the Log Cabin. Old Mr. Kindig was still alive. I put together my own flintlock. Some years later here in WV my mainspring broke. No chance in finding another. I made my own and some 34 years later it is still going strong. I also made a new frizzen spring for another lock, still working. I love files and hacksaws!
Cheap oil hardening tool steel, harden, throw on top of lead in pot set at 600 degrees and let float for an hour. Fish it out to set on pot edge, shut off pot and let cool slow.
Make sure all scratches are gone before hardening.