Testing .22 Rat-Shot Ammunition

22 long Rifle shot ammunition is useful for dispatching rodents and pest birds inside barns, as well as for taking out snakes. It's loaded with "dust shot (#12 or #11 shot) I've heard lots of stories about how the stuff works so I decided to pattern test Winchester and Federal .22 long rifle shot to see what it really does. Does firing it from rifled barrels really give a ring shaped pattern? How far back is it effective? What's better, a short barrel like those on handguns or is it better to have a longer rifle barrel? Will it cycle in semi-automatic? The only way to find out is to try it.