folically C: I too have experienced, 2 I believe, old 70s vintage RCBS dies that apparently were just incapable of producing straight ammo. In one case, they did an exchange for a new one and the new one was MUCH better. Actually I've had problems both in the sizing and seating re: concentricity. I think most common wisdom has been that most concentricity issues are from sizing, but my experience is with both. With the last go-round, it was with seating, and that was using a Forstner bench rest seater, BUT, after a bunch of trying different things, it ended up being with the brass. New starline brass came out just fine.
Good observations.
I have mentioned this before, both here and in my books, but there was a period in the 1970s when RCBS made sizing dies for cartridges on the same basic case by first reaming the body of the die, then separately reaming the neck portion. As a result, dies for the .25-06, .270, .30-06, .338-06 and .35 Whelen (or anything else based on the '06 case) could have a neck misaligned with the body.
If so, it was IMPOSSIBLE to resize cases so the neck/bullet was aligned with the case body, even if you "squared" the sizing die with the press, or used really uniform brass. I know this partly through a gunsmith well-known for making "accuracy" rifles, and partly through testing a couple of sets of RCBS dies I bought during the 70s--one for the .358 Winchester purchased in a local store, the other a "custom" set of .338-06 dies ordered directly from RCBS when I was in college--which cost almost as much as my tuition for that semester. Eventually acquired a concentricty gauge, and found EVERY case sized in those dies had a neck out of line with body.
RCBS apparently abandoned that practice sometime in the 1980s. Haven't encountered that problem since then..
