Some years ago I was tinkering with my Narragansett Early Virginia. It has the Chambers colonial lock and uses a 7/8 flint. I primed with 4f, 3f, and 2f and my human senses could tell no difference in the lock time. I'm sure one of those high speed cameras would pick up some difference, but I couldn't. Most modern day shooters, including me, probably use a separate priming horn, especially on a range. I read some years back no separate priming horns have ever been found in surviving possibles and hunting bags, which would seem to indicate Daniel Boone, Lewis Wetzel, Simon Girty, and their peers primed from the main horn.