I just conducted my own two year test of primer seating in actual competition. Brian " The Witch Doctor" mentioned some things in his podcast that seemed plausible. Being the my real name is Thomas and a true doubting Thomas at that, I had to test this for myself. After two years of testing in actual matches around Texas and now South Carolina, my best results according to two years of data points to having the print just seat on the pocket floor to .001 of crush. When oover seating or crushing the primer, the rifles would spit shots into the conditions randomly.
That's all I got,
Keep'em small!
Speedy
PS: I use a Sinclair 2000, I have had for years with the addition of the Second Hand to hold it vertically on my loading bench.. Watch the video and start about minute 38 to see it live.