Took longer to type this than it took them to act after talking to them.
I hope it works out, I purchased a Winchester Model 70 chamber to 300 Win Mag with the ugliest chamber I have ever seen, Like you I called them I told, them the chamber was too large in diameter and too long from the shoulder to the bolt face and the chamber was gouged. They made arrangements for me to take the rifle to their warranty smith in the area. When I delivered the rifle I thought it would be a help if we discussed the problem with the rifle. He claimed Winchester had given him instructions on 'how to repair'. Winchester instructed him to hone, polish and or ream the chamber and I asked "How is it possible to reduce the length and or diameter of the chamber with a hone, reamer or polishing.
2 Months later I went to check on the rifle, the smith said they returned the rifle to Winchester, I had to ask 'why?', he said the chamber was to long and too large in diameter and had long gouges. It was about that time I asked did that happen when he honed the chamber or when he reamed the chamber, he said no, the chamber was like that when the rifle came in. Anyhow, it did not get better, they did sent the rifle back in a new box. I ask Winchester for a chamber that fit my dies or dies that would fit their chamber. That had to be 14 years ago, I dug the rifle out with ever intent to load 100 rounds and head for the range, I changed my mind when the bolt would not close on new, over the counter factory ammo, the bolt would not close minimum length/full length sized cases. I propped the rifle up in a corner. that was close to a year ago.
I understand Winchester got out to the rifle and ammo business in 1929, and then there was Browning, there had to be a reason he had his rifles made in another country.
F. Guffey