Dumbass kids we wuz....
We found that you could take a 1/4"ID pipe and crimp the end just slightly. Now a .22 round fits in nicely. Since it's a rim fire round, all ya gotta do is squat down, pipe vertical in one hand and bang that sucker on a rock and away it goes... straight up or whatever angle you managed.
Now, tell me how I still have both hands?