Well, I used to shoot plastic BB’s at the squirrels on my mom’s birdfeeder. It got to the point where I had to use my brother’s semi-automatic BB gun because the squirrels quickly learned that the sound of me cocking the BB gun was quickly followed by a plastic pellet to the hindquarters. I don’t know whether it hurt the squirrels or just startled them more (it mildly stings on bare skin, and the squirrels had all that fur).