As to this being scope/mount related, I have recent history with that problem. In fact the way the Mauser from Hell got its name was related to this. Because the previous smiths had boogered the rear screw hole, the POI would jump around. I'd get 2 or three close together, and then I'd get a group over here and then over there. The POI jumped until the scope got knocked loose and then it would point to a new spot for a few shots. Supposedly the scope and mount are straightend out now. Before, the rifle never returned to a previous POI.
Pitting did occur to me. When I first got the rifle it was badly fouled with copper. I removed the copper, scrubbed the heck out of the barrel and then applied Dyna Borecoat. Yes there is probably a pit here and there.
Last edited by shaman; 09/18/17.
