primer seating depth, flush with base, causing misfire problem?

[Unclenick]

Originally Posted by Gwpercle

Seat them till they hit bottom of pocket. Don't worry about measurements or how deep they are seated. I prime off press with a hand held primer tool so I can feel when they bottom out

Benchresters used to do that until the late Creighton Audette figured out it didn't give best consistency. His last writings were on this topic in Precision Shooting in 1994. Federal says to seat their small primers 0.002" deeper than the point at which they make contact, and 0.003" for large primers. This is called setting the bridge (the amount of priming mix bridging the gap between primer cup and anvil). Olin and Remington give 0.002"-0.006" for all primers.

"There is some debate about how deeply primers should be seated. I don’t pretend to have all the answers about this, but I have experimented with seating primers to different depths and seeing what happens on the chronograph and target paper, and so far I’ve obtained my best results seating them hard, pushing them in past the point where the anvil can be felt hitting the bottom of the pocket. Doing this, I can almost always get velocity standard deviations of less than 10 feet per second, even with magnum cartridges and long-bodied standards on the ’06 case, and I haven’t been able to accomplish that seating primers to lesser depths."

Dan Hackett
Precision Shooting Reloading Guide, Precision Shooting Inc., Pub. (R.I.P.), Manchester, CT, 1995, p. 271.