I primed 10,000's of thousands on a Rock Chucker press, and many more than that on an RCBS and now a Hornady hand press. Never had one go off. Like gr8ful, I did have one go off with a vacum sweeper.
I have a small remnant of carpet in front of my bench. Decided on day, to vacum it. Bought my old Hoover sweeper down stairs, and proceded to sweep. When that baby went off, not sure who moved quicker, me, or my dog. Scared the crap out of me, and I don't think the dog touched the strairs on the way up. She was looking down at me from the top of the stairs, with that, what in the hell did you just do look. I was laughing as I removed the bag from the vacum, as I was afraid the primer might start the dog hair on fire in the bag, which it didn't. Now I take the carpet outside and shake it. gypsyman