I'd be curious to know, not first hand though, what exactly it takes to get a primer to go of on the deck of a press. I'm wondering because I certainly mangled, and I mean completely destroyed, a few primers when I started out. I was shocked to see the condition of the destroyed primers. I was surprised they didn't go off. Maybe I wasn't pushing the handle back fast enough to get a reaction? I go easy on the back stroke (primer seating on a 650) as a precautionary measure.