Electrochemical Rifling barrel, maybe we are on the right track.

It is my understanding that S&W went ECM on their revolver barrels quite a long time ago. The general response was that cast boolit shooting took a hit. I do not know if that was due to ECM but can absolutely say my older revolvers do better with cast than my newer guns.

I've done the cast boolit thang for a very long time and suspect that there may have been some other changes at the same time. I'm not a practicing metallurgist but do have a BSc and would most definitely expect that they changed alloys of their barrels to optimize the ECM process. OR, maybe they are too smooth?