Practice. Then, practice a lot more.
I second that ... with a sling shot - practice - practice - practice is required ... I use 3/8 inch steel nuts as projectiles ... when exercise walking to ward off the occasional dog. The hollow center steel nut seems to whistle at a sound beyond human hearing hearing. Even when I miss the dog is more than willing to retreat even upon my mere appearance on the road... Pavlov’s dogs...
With practice many small mammels or birds could be prey... but it takes a lot of practice ...