My grandfather was a gun smith and he hated going outside in the winter to test out guns so he had a thick stack of old phone books in his basement outside his

My grandfather was a gun smith and he hated going outside in the winter to test out guns so he had a thick stack of old phone books in his basement outside his gun room and he'd fire into them semi regularly while building/repairing guns. Those phone books would easily stop even semi 'serious' rounds.