No need for mythbusters. It has been tested by the FBI, the Military and dozens of law enforcement agencies for at least 100 years. They all come to the same conclusions. Birdshot usually works OK at near contact ranges. It does not reliably give enough penetration to get to vital organs, especially if it has to get through heavy clothing like denim or leather jackets.
Every law enforcement and military agencey uses buckshot if they want to limit damage to innocent bystanders. There are different sizes of buckshot if you feel the threat of 00 buck is too much. I have no problem using whatever you have. It just seems like a bad idea to plan on birdshot as your 1st option.