Who needs that hard to find .22LR ammo anyway. Everything is going sustainable, and you can't get much more sustainable than home grown ammunition.
Yes, higher powers are showing an interest in the potato gun.
Potato guns are air cannons. Back when the best thing they could put in a shell was dynamite, they used to use really large air cannon to slowly accelerat the shell down the barrel. New York was protected by a large (10" caliber ? I think) air cannon that would lob TNT at any invaiding fleet. So the idea of air canons is sort of a new, old idea.
What is a little new is the potato thing.
US Air Force Measures Potato Cannon Muzzle Velocities
MIT Technology Review, 8 May 2013 (hat tip: MR)
The workhorse projectile launcher for physics demonstrations and a certain kind of hobbyist is the potato cannon. A common design involves using compressed air to accelerate a lump of potato out of a tube...
But a question that will have passed through the minds of many hobbyists is: what is the best fuel for a potato cannon? Today, they get their answer thanks to the work of Michael Courtney at the United States Air Force Academy in Colorado and another Courtney at BTG Research in Colorado Springs.
I guess the way to go is with acetylene.