It would be devistating inside of 10-15 feet, past that it spreads it's small pellets too far apart to help insure any pentration. The biggest bird shot I would feel comfortable with is #4 bird shot, even then heavy clothing would restrict some of the penetration, but I would use it inside of 30feet and feel comfortable. I have used the same #4 to kill fox out to 45 yards with the pellets penetrationg to 4" through meat and a few pellets pentrated into the skull. Better yet would be #2's or BB's for self defense.