Shot this video of a friend firing his .50 cal flinty last weekend. He'd played with the amount and type of powder in the pan to slow things down a little for effect. Thought you all might a look.

I'm glad you said he played with the pan powder to slow things down. Otherwise that would be an unacceptable delay between pan ignition and charge ignition.

After much experimentation with the amount of powder in the pan and/or its location in the pan in my guns I found pan powder level across the pan below the bottom edge of the hole works best. If adjusting the pan powder doesn't improve things the touchhole needs enlargement.

Semi, it would be interesting to have a cap [side lock] and a modern sealed inline taken at the same speed on with the flint lock. Some seem to think there is no lag.

Not nearly that much lag with a properly made flintlock...

I've been shooting flinters since the early 70s and I had a few that were slow (delayed) no matter what I did to them. I've also had a couple were here was no perceivable delay. I hung onto those and even have an extra lock.

Not sure what he did to slow things down. Any ideas on what he might have done?

Probably overfilled the pan.

All you have to do to slow one down is cover the flash hole with powder then it has to burn down to the flash hole to set off the charge.