Found this video a few days back. He seems to be making the assertion that having copper in your bore is desirable. That it creates a smoother surface to travel on, and protects the barrel from corrosion, among other things. To me his reasoning seems somewhat anecdotal and circular. My understanding is that there are layers of carbon and copper, kind of like a lasagna, that build up. And his assertion that he has shot better groups at the end of a 60rnd session could just be due to him warming up as a shooter.
Lots to unpack here.
https://youtu.be/rAQaxIlQukU
Lots to unpack here.
https://youtu.be/rAQaxIlQukU