From what I know about custom aftermarket barrels, and I have used quite a few -Hart, Lilja, Rock Creek, and Krieger, they get 20 ft steel bars from the mill in bulk. If the steel is sub-par it would show up on other barrels in the same production lot. Sometimes a blank has an occlusion that shows up during the deep drill or rifling process, but that is not the problem in this case. I would imagine the mill provides the barrel maker with the complete metallurgical analysis on each lot received, but I don't see where metallurgical test on one barrel will differ from the analysis on the lot received. I have one of the first 300 RUM's in a Rem 700 from the custom shop and use it sparingly because I know accurate barrel life is limited. I knew this going in when I bought it and as such I check throat erosion often.