5ft or less in .22 any thing more would be a stunn, speaking from first hand experience... ive killed mice that have happened to run by and shot a birds who wouldent stop pecking at my chimney... shot at the bird hit the bird watch the bird fall, walk over to the bird to make sure the job was done and the bird got up and flew away haha... to this day still pecking at my chimney on occasion haha, he won that round...