My first foray into slingshots was the quintessential forked stick with straps of inter-tube connecting a leather pouch. Gravel was the ammo. It wasn't much but it piqued my interest. It wasn't much later that I purchased a Daisy wrist rocket and graduated to ball bearings.
I ran through several slingshots and I can't imagine how many bands (though I would make all kinds of repairs to a broken band to keep it running as long as possible).
I like to think that I got pretty good at it. A 12oz can wasn't at all safe within 30 yards. I likely wouldn't make it on the first shot, but it also wouldn't take many attempts.
My favorite "shot" was a fluke but I never admitted it involved sheer luck to those who witnessed it. I was about 12 and spying a toad sitting by a tree from a friends deck quite some distance away (it was long ago, but 20 yards sounds about right). I dug into my pocket to fish out anything heavy and round, but there was only one item left, a heavy washer. Not the kind of "round" I was looking for.
At that point I just wanted to "make some noise" as flat items would often make a ricochet sound in flight. My friends, with pellet rifles, were telling me to dream on; the shot was impossible. I hadn't told them I really wasn't trying for the toad anymore but rather wanted to surprise them with the strange noises flat projectiles would make.
So aiming at the toad, I let loose with the washer, not at all expecting to come close.
The washer took on the expected erratic path through the air, first veering left, then abruptly right. Disappointingly, it generated a very weak whine. However a second later, the toad looked to have stood up and fell backwards. It was struck squarely between the eyes.
Those of my friends who could pick their jaws off the floor made comments of wonder braced by words a kid really shouldn't be saying. Yes, it was absolute chance and there was zero skill involved but to this day, should any one of them bring it up, I will echo what I said back then with the same straight face..."piece of cake".
I have recently purchased a Pocket Shot with wrist brace attachment (pocket hammer?) along with some of the red replacement "pockets" and 1/2" steel bearings. If ever I get the time, I may see how it compares to the old wrist rockets (which I still own a few of).