Erik Cortina has a video where he anneals brass then measures seating presure with a gauge. After annealing the seating pressure varied somewhere around 10-20 lbs. No uniformity. Pushing harder might make the seating cup move a little farther down the ogive? I would think the distance of the bearing surface to the rifling is what's important. That should have some affect on the shape of the pressure vs time curve. The pressure isn't determined by where the tip is. Bullet jump determines approximate bearing surface to rifling then we use a method to seat bullets based on that measurement. Short range shooters shoot extremley small groups by measuring jump then seating with a die that must be like what all of us are using. A lot of SR shooters are using neck wall thickness around 0.0085" so they have less tension to force bullets in the case. Sorry if I am wandering but these are things I thought of.I checked the seater stem last night when I got home from work, inspecting it with a magnifying glass and good light.
There were clearly no cracks on the stem, I then turned it over and put a bullet in the stem pressing down on it and still no seperations.
Next thought is to try some other brands of bullets, I have some Bibs to try and some Barts.
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