Not much could have been done with the potato flinger, either. Even back then, not many people had access to a hill of potatoes.
The sling, though, was something else again. War was just around the corner, but we were still in the pacifist '30s. On maneuvers, the U.S. Army sometimes had to use broomsticks for guns. As for small boys, their weaponry was woefully inadequate: mock Frontier Revolvers made of wood put together from kits, plus a handful of Buck Rogers Rocket Pistols and a few decrepit Daisy Air Rifles.
Even today, what with all the talk about the need to reemphasize conventional arms, I'm sometimes teased by the thought that, commercially, such a slingshot might still be successful. In place of scarce (and dangerous) stones, city kids could use bubble gum, or some softish, marble-sized projectile, specially designed to explode harmlessly upon impact, releasing fake smoke or a fortune-cookie ribbon with an appropriate sentiment (Make mess, not war?). The stone sack would not be made of leather, but out of thin plastic, stamped with a catchy product name for TV: SLINGIN' SAM, perhaps, or SLAM BANG! or maybe something truly awful like LI'L DAVID.
On second thought, maybe not. Better if all those flying stones just keep zinging their way into the woods of memory.