How did they cast barrels?

[IMshooter]

I've been enjoying this website and it has rekindled my interest in cannons.  So I have been wondering, how did they cast cannon barrels?  And what I really mean is, what did they use for the mold?

I'll have to post a photo of my cannon sometime, too.  In high school metals class I made a .45 cannon barrel on a lathe (now-a-days one would be arrested and kicked out of school for a year!).  It sits in a wood ship style carriage and I usually shoot it as a noisemaker, but it also fires .45 acp slugs nicely.  Granted, there is no rifling and accuracy is terrible.

[GGaskill]

Look at the One of my 1/2 scale mountain howitzers thread for a discussion of small scale casting.  Doing larger ones is mostly just scaling everything up to the appropriate size.

[IMshooter]

Thanks for sending that thread.