Change my mind for what? Did you not actually read my first post on this subject?Obviously I’m not going to change your mind. I don’t want an unclean able groove in my breech plug.
Don’t care if that works for you.
The old adage applies here.
My mind is made up, don’t confuse me with facts.
Historically they often enough grooved plugs and those arms functioned well. So its not wrong. “Do it right” does not apply, “Do it better” does.