A guy showed up at the shop yesterday with a model 70 classic in 300 WSM saying he was having inconsistent problem with chambering full length sized rounds. I went through it, checked the settings on his sizing die, bolt clearance in the action, extractor clearance, headspace check, etc, all checked out OK. Could not come up with an answer so decided to pull the barrel. When I did, I put in my reamer and turned it by hand. I could feel it cut a small amount, pulled out the reamer and guess what, two shiny spots in the chamber near the back on opposite sides. THE CHAMBER WAS OUT OF ROUND!
The rifle belonged to his brother in law and he only shot factory ammo and had shot it for years that way. The deal with not fitting, if he took a full length cartridge and tried it in the chamber, unless it was oriented the same as when it was fired, it would not fit. How did Winchester cut a chamber out of round???
Jim
