I know from previous discussions that JE Custom prefers Lilja barrels. So if their barrel bores are true within .001", that would re-enforce what JE was saying.
Everyone has there favorite barrel maker and I have mine. The reason that I prefer one over the other is =
Consistency from barrel to barrel, quality (How well they stay within advertised tolerances), brake in ability and foremost there consistent accuracy.
The original poster ask "why dial a rifle bore in within .0001". somewhere this question was lost in a debate as to weather a person could even do it or that barrels were not manufactured close enough to even try.
My Opinion is, ''You must try'' because how else are you going to know what quality you are getting
from your barrel maker unless you test it before you proceed with the build.
There are many ways to do this testing and the way is not as important as the results. just because someone said it on the internet doesn't mean it is true. the only way is to prove it is with testing.
There was also some discussion about out of round or improper size bores. there is a very simple way to find out if you have this situation with reamer pilots. When I buy a piloted reamer, I like to get the standard pilot(For a .338 the pilot diameter is .3292) the next size larger (Tighter) is normally .3294 and the size smaller is .3290. and if you purchase these also, you can test the bore
size with these three bushings. If the bore is larger or smaller than these bushings I personally elect not to use the barrel and send it back. If I have to send a barrel back, the barrel maker is given one more chance to MEET HIS SPEC. and if he doesn't I just don't use any more of his barrels. I re barrel for my self and a few friends and don't have to except marginal quality.
So my limit is = +or - .0004 on roundness and bore diameter and .001 max on bore straightness.
NOTE: this has nothing to do with contour alignment with the bore. That is a different test and requirement for me. Other people have different levels of acceptance, (Some less and some more) and as long as they are happy with what they find, all is good.
So again, "YOU GET WHAT YOU INSPECT. NOT WHAT YOU EXPECT"
J E CUSTOM