I think you are referring to the small reloading kit without a press. A hammer is used. I had one of those years ago and remember popping a primer when I struck too hard with a hammer. Never had a primer go off when I would "tap tap tap", (as instructed) but a "smack" will give a crack. Not much more than a scare but that was bad enough. I doubt any primer would stand up to a good smack, or it wouldn't be trustworthy. I'd just tap, tap, tap, with a small hammer if I were you.