I don’t have my wound ballistics references here with me at work (and in fact I think they’re stored away into one of an anonymous series of boxes yet to be unpacked from the latest move) but while not the most scientific of studies, the Box O’ Truth has a specific comparison between the effectiveness of buckshot and #8 birdshot out of both a 12 gauge and 20 gauge shotgun which strongly supports the contention that birdshot in either gague does not offer adequate penetration to for effective and immediate reduction of a threat. Note that at 15 feet against a denim outer layer the shot from either gun did not penetrate more than 6" into water, which would be about 3-4" into 10% ballistic gelatin or soft flesh. This simply isn’t enough penetration to ensure that a center of mass hit would reach vital organs or nerves. The FBI minimum penetration criteria for handgun effectiveness is twelve inches (13.5" into 10% gelatin), which will assure that the bullet or pellets can penetrate the lungs or heart. The major difference between the 12 gauge and 20 gauge is (unsurprising to forensicists) is not the penetration depth but the area of damage; the 12 gauge carries more pellets and therefore has a wider (but not deeper) area of damage. While handloaders widely look at muzzle (kinetic) energy as a measure of handgun “power”, for terminal ballistics the key factor is penetration, which is really dependent upon momentum. Until you get to the hypersonic rounds, hydrostatic shock doesn’t play a significant factor in stopping potential; effectiveness is limited to the permanent wound channel formed by the physical passage of the bullet. (This also argues to a lack of persuasive argument for the effectiveness of one major caliber over another, though I still like the .45 ACP over smaller rounds for more controlled and reliable expansion.)
Martin Fackler and Duncan McPherson are the two pre-eminent authorities on terminal ballistics, and why they have some disagreement on particular issues they are both agreed on the above point. The [URL=http://www.iwba.com/]Internatinoal Wound Ballistics Association* publishes Wound Ballistics Review, the major journal of forensic wound ballistics. I don’t know of any FBI studies on the effectiveness of birdshot because no credible law enforcement agency would use such a load, being neither effective nor non-lethal/maiming enough to be useful.
Again, if you are going to put sights and drop the hammer on some evil-doer, you have decided that the perpetrator has done something that threatens your mortal well-being or that of your friends and family, and should use the most effective means feasible to stop the threat expeditiously without posing excessive hazard to bystanders. Birdshot doesn’t meet this criteria in any way.
Stranger