How clean are your revolver throats? Even a little fouling in a revolver throat can cause chambering problems. If you have .452 throats, and .452 bullets, there's no room for fouling from previous shooting. Back in Elmer Keiths day, Lyman reduced the diameter of the front driving band of his bullet designs to facilitate reloading dirty chambers. This is one of the things that really upset Elmer, who rather enthusiastically let them know what he thought. Another possibility is that you over flared your cases, and that your crimp die wasn't able to remove all of the flare. This would show up as a slight bulge in the case, just below the crimp.