Called S&W CS today to tell the about erosion on the face of the barrel next to the forcing cone. There is no top strap or cylinder erosion. The CS rep (Steve) thought it could have been the ammo I use, mostly 125 JHP. It's SN CTX7*** so it's fairly new with 500 to 1000 rounds thru it, probably 1/3 DA. The factory also had it for several months to do the "Master Revolver Action Package". The number on the box is 3057, but I don't know if that's 2003 or 2013. I'm thinking 2013. Any thoughts on why this happened and what ammo would prevent it from happening again? Steve (who was very nice and cooperative) emailed me a shipping label to send it back for examination, which I did. Any help would be appreciated.

Wish you would have posted pictures. Checked my 2013 vintage 686P and its perfect after a couple of thousand rounds. Good luck and let us know how it turns out.

Would shooting 9mm ammo through a 357 bore do it? Would the uncertainty in the position of the narrower bullet move to one side and hit the forcing cone?