Gunner Asch wrote:

I thought that most arty of that size was driven by copper driving bands
rather than rifling graving the case of the round?

That would make sense to me, and the NIST folks were not revealing
everything about the project.
So, I really don't know what the real story was. It is possible it had
nothing to do with the barrels, and everything to do with armor piercing
qualities of the round.

Jon