Try resizing another piece of brass and don't prime it or seat a bullet, then see if it chambers. That will at least eliminate the bullet as a cause. I know they both fit fine in your go/no go guage, but it still sounds like a case issue. have you checked the size of the rim? Perhaps a thick rim could keep it from closing.
Guns don't kill people, fathers with pretty daughters do.
Two wrongs don't make a right, but three comes pretty close.
Proud NRA member