Shoot, now I've a diagram of an aimable bank of pipes dancing around in my head. Not for the assinigned purpose of shooting at helicopters of course, but it would be neat for the fourth of july, shooting up "strings" of bottle rockets.
I've heard for multiple firings the bottle rockets are placed around the mouth of the pipe with their sticks in the pipe and a propane torch is held to the fuses as the pipe is rotated as fast as the fuses can be ignited.............................................. at least that's what I heard.