I have had this revolver for a couple of weeks for testing and deciding what to do with it,it anything. I have fed it only FMJ Magtech factory ammo, about 600 rds. The gun is full of problems,a customer return,it is cheap now so I decided I will repair it.
(Being overseas,no S&W warranty here).
Today I decided to switch to my own cast and started to give the gun a serious deep clean first - I have removed copper every 100 rds or so. Well there was lead coming out, a clean VFG plug gets gray stripes no matter what. I didn't use vinegar/peroxide yet. But I already noticed that the previous owner had fired cowboy ammo,there was lead under copper.
There still is lead.
So I took some pics and wow,there seems to be a narrow,little extra groove on the edge of the rifling groove,collecting whatever gets there first.
What is causing this and why?