Dozens of countries
The first were made from bamboo, which is a type of grass.
Wooden barrels are made by a Cooper, and that is largely a hand craft. Steel barrels are made in a sheet metal shop, as this workplace is called, and this process is fully automated.
The original Gatling gun had six to ten barrels which rotated and fired independently. This was one of the earliest machine guns made.
The same thread pattern as a Belgium made Browning. Same gun, same specs, different metal in the barrels.
Watertable, forearm metal, and barrels
They made the large wooden barrels which were used to store a variety of things. More specifically, they made to metal bands that encircled the barrels.
I'm not sure exactly what you're asking here. Generally a shotgun with Damascus barrels (those showing a spiral pattern on the outside, since they were made from spiralling layers of metal) will have been made for black powder only. In their time, fine Damascus barrels were considered a superior option, but caution should be exercised shooting such guns now, and definitely only black powder should be used. If in doubt, get the gun checked by a qualified gunsmith.
The very first ones were made with bamboo. ********** Later barrels were cast of brass and bronze. Iron barrels were made by heating and twisting strips of iron or steel, reheating, twisting around a rod, reheating, and hammer welding.
No. Cast iron is brittle, and shatters like glass.
Gatling gun
steel