Some projects just don't work out no matter what you do. If you can take a step back for a little while it might help. I had a recent project go like this and I ended up throwing it on a shelf for a year before looking at it again with a fresh perspective. I went a completely differently direct with the bullet I wanted to shoot, tried a powder I wouldn't normally use in a case that size, and ended up being happy with the results.
If all else fails, run a 30/6.5 RPM reamer in that chamber and give it a go.