I haven't attempted to play a shotgun, but used to give the kids each one fired (empty) .38 Special, .410, 12 ga, or '06 cartridge case to use as a signal whistle when wandering around primitive campsites. The cartridge cases generally produce a pretty shrill tone that carries for a long distance, and it's easier for most people to tell the direction a sound comes from when higher pitches are used. With the larger sizes, overblowing to 2d & higher harmonics gives a selection of notes or note combinations that can be used to signify "just lost," "in trouble," or "come and see the rotting 'possum corpse, I just found," but the kids never conformed well to our prearranged codings.

I toyed with the idea of "pan pipes" made with cartridge cases of selected sizes, but never accumulated a sufficient collection of different sized cases to make much of an instrument.

(I did find my souvenir 105 Howitzer casing a bit difficult to blow. It would perhaps be better suited for use in a king-sized glockenspiel(?).)

John