The only difference between a bell and a crude howitzer is the quality of metal.
Longer cannon require some slightly different methods, but even howitzer is vastly better for siege warfare than catapults.
Not for naval use though, for those you need true cannon.
Rifling is usually done after casting, and the spirals involved are not as "tight" as you seem to think. Its usually done with a type of drill bit. Modern rifles can use a lining "sleeve" of different material than the barrel, but thats not necessary.
Check out the picture in the upper right here:
http://en.wikipedia.org/wiki/Rifling
It would make much more sense if the fire nation had secretly forbidden "gun" research, than that they lacked the tech base to make them.
It may also just be an outside context issue too. Especially since human flight came about under direct human power in this verse.
It's not that big a deal that they might have overlooked the idea however, and its not enough of a wall-banger that I can not ignore it for the awesome story though
Longer cannon require some slightly different methods, but even howitzer is vastly better for siege warfare than catapults.
Not for naval use though, for those you need true cannon.
Rifling is usually done after casting, and the spirals involved are not as "tight" as you seem to think. Its usually done with a type of drill bit. Modern rifles can use a lining "sleeve" of different material than the barrel, but thats not necessary.
Check out the picture in the upper right here:
http://en.wikipedia.org/wiki/Rifling
It would make much more sense if the fire nation had secretly forbidden "gun" research, than that they lacked the tech base to make them.
It may also just be an outside context issue too. Especially since human flight came about under direct human power in this verse.
It's not that big a deal that they might have overlooked the idea however, and its not enough of a wall-banger that I can not ignore it for the awesome story though