B/c the chamber size severely reduces the charges in c/b revolvers, once wads are included, there's not much room for shot. Other than #9 or "dust" shot, you could probably count out pellets. Modern pistol cartridge shotshells are sold for "snake" loads mostly. Rat, mice, sparrow ammo - not rabbits & squirrels. A few used a couple of buckshot. "Garden Guns" were popular years ago - mostly rimfire 9mm, etc.
Trick shootists back in the day used pistols loaded with shot for flying targets and also there were shotshells intended for riot control sold that would cycle in Thompsons. Smokeless powder give more room for shot than black.