In all seriousness (if that's possible in this sort of thing), I've heard music (?) played by folks using gun barrels as instruments. The disconnected ones, open at both ends, were played like trumpets; the closed ones, like on a flintlock, were blown like bottles. Varying lengths gave varying tones. No, they were not loaded.

Hunters in some sections of the US used to use shotgun barrels as hunting horns.