I just got back from Conner Prairie and thought I better get in on this discussion. The initial motivation for this last batch of experiments was to look into high vs low vent locations. The location of the prime in the pan took off when I wanted to eliminate variables. Close to the vent is indeed faster, around 15% in one set of trials. However, as a number of you suggest something measurable in a lab isn't necessarily noticable with human senses. (My first conclusion was that human eyes and ears are terrible tools to use in this instance.)
Another issue is that in my tests I took much greater effort to place prime than a shooter in the field would use. In my tests perhaps 2/3 of the pan would be empty in order to measure each portion of the pan. I could get away with this because the prime would be ignited by a red hot wire. Obviously a shooter needs powder under the sparks - that changes everything.
My biggest surprises in this set of trials were that:
Banking the prime away is slowest.
High/low vent position makes less difference that we thought - practically no diff.
Actually covering the vent does not slow ignition. (Filling the flash channel on a non-liner vent hole might be slower; I did not measure that.)
Here is a link to the intro of the testing:
http://www.blackpowdermag.com/featured-articles/pan-vent-experiments.phpParts 2&3 demonstrate that the closer the fire is the more intense. Part 2 looks at burn marks, while Part 3 looks at fire through the muzzle.
Part 4 deals with the amount of prime. In my L&R pan 3/4 grain was faster than 1 grain.
Part 5 deals with prime location.
Part 6 deals with high/low vent location.
Thank you for comments.
Regards,
Pletch