We have done tests with various birdshot loads. Birdshot penetrated through two pieces of drywall (representing one wall) and was stopped in the paper on the front of the second wall. The problem with birdshot is that it does not penetrate enough to be effective as a defense round. Birdshot is designed to bring down little birds.

A policeman told of seeing a guy shot at close range with a load of 12 gauge birdshot, and was not even knocked down. He was still walking around when the EMTs got there. It was an ugly, shallow wound, but did not STOP the guy.