the bullet didnt come out??? thats odd between the inertia and the pressure from the primer should have spit that bullet right out. My guess is if the primer went off you maybe seating your primers to deep to the point where they are crushing thats about the only thing i can think of that would cause a primer to be unstable like that. Ive pulled hundreds of live cartridges with a inertia bullet puller and never had any problem.