I believe the fluted chambers as found in the H-K rifles are formed as a part of the hammer forging operation. Regards, Bill.

Sounds like a chamber wherein the reamer had chattered. It happens. Regards, Bill.

It was probably and old junker Win. All the indications of headspace and a corroded chamber...Lots of old Winchester lever guns have headspace problems. What you see on the case is a duplicate of the chamber in reverse...No, its not rifled, just basically rotted out IMO......

Win. lever and Savage levers are considered "springy", but they perform just like they are supposed to with correct loading techniques and proper care...Many of the guns are tight as a tick and 150 years old and still going strong...