Although the rifling looks pretty good I just couldn't get a repeatable twist reading. I'll try again though.
Looking at the dimensions in my Lyman #49 for the .25-20 WCF and comparing them to my chamber cast, the theory that someone ran a .25-20 through seems to be plausible. I'm going to ask around to see if anyone has a fired .25 WCF case they could loan me to see how it fits.
All this said, any thoughts/recommendations on what to do? Ream (correctly) for another cartridge? Ream, line and cut for the original cartridge?