"Slam Fires"? How often do they occur? What precipitates it? Which rifles?

bolt-action rifles rarely have a slam fire this would be something that more than likely would happen in a semi-auto, but I am not saying it could not happen with a bolt-action, being a beginning reloader you might want to make sure each rounds primer is seated to the full depth in the primer pocket, and is actually below the head of the case and if you can cycle your rifle with the safety on which is a good Idea when checking if the rounds will function reliably through your action, another choice would be to remove the firing pin completely and then, there would be no way a slam-fire could occur at all! have fun reloading and remember safety first when handling primers, powder and firearms