My perspective: The noteable problem, and the customer base turn-off, with the OP's experiences with Proof is not that they send out a number of poorly QA/QC controlled bore diameters. He never claimed every barrel should be perfect. He was communicating with Proof, trying to work through the problem.
Proof decided to blame his chamber, rather than improve their QA/QC control, over the diameter of their bores. And then ceased communications altogether. Pretty sure elkaholic's goal was to resolve the ongoing issue so his customers could feel good about purchasing and using Proof barrels, with his positive recommendation.
His experience with Proof barrels directly, or thru feedback from clients and their chosen gunsmiths, may exceed the experiences of all others responding to this Thread, combined. This is clearly not a case were only one, two, or even several, bad barrels were identified.
So the excuse no barrel manufacturer is perfect, or it's normal for barrel manufacturers to have a few bad barrels slip thru QA/QC, doesn't apply. Isn't a legitimate excuse.
Lots of examples where a company establishes a domineering share of the marketplace, and then fumbles. Drops the ball.
Leupold scopes come to mind. Kept making money with sub-par quality optics for quite a few years, based on their prior US marketplace dominance alone. Thankfully, they seem to be back in the game again, competing well, with improved optics.
Remington's management never learned, cared, or both. Hoping Rem Arms has learned from prior Remington management's mistakes, and maintains a successful business.