Tests show that with flintlocks...
Tests conducted at Colonial Williamsburg showed that when the flint strikes the frizzen, the frizzen doesn't merely fall back and release a shower of sparks. The frizzen actually bounces forward and recoils back several times, sometimes even striking the flint. The sparks are (as we know) small particles of metal that are scraped downward towards the priming charge. They are so small that some sparks actually bounce back out of the pan without igniting the powder. They concluded that larger grain powder actually ignites better than finer 4F powder (news to me).
This film which featured several locks (both period and modern flintlocks) was filmed quite a few years ago and was shown to interested students during the NMLRA Gunbuilders' Workshop at Bowling Green, KY.
If they ever get their hands on another slow motion camera, they want to test the location of the touchhole and see what works better for ignition.
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