If it's worked for 27 years, and you ruled out the ejector isn't catching, the brass not bad, a base mount screw not protruding into the chamber, and the chamber not dirty, then I'd say you have a bad problem!!! You do mention blackened cases! In this case I'd suspect a blackened chamber also. Sounds as if it needs a darn good cleaning!!!! I wouldn't think the flame cutting like happened in the revolvers is going to happen in a TC barrel.