Years ago an injured stray cat had taken refuge in a spare dog house on my dad's property. He decided to put the cat out of it's misery and use the .22lr shot shell out of his Colt Scout Buntline. His thinking was he didn't want a 40gr. bullet to penetrate the cat and damage the dog house
He made a head shot from about two feet. All it did was piss off the cat which took off at a high rate of speed
. The cat was later picked up, still alive, by animal control (that's another story). I don't think those shot shells are worth much good for any thing.