Dave: From my personal journey with an Encore barrel of mine, also in .243. I was hard pressed to find a factory load that would shoot 3 shots under 2" consistently. Spoke w/ T/C and after they assured me that anything under 4" with factory ammo is a good shooting barrel they had me check fired case sizes as they "occasionaly" see problems with oversize chambers. Apparently it only happens so infrequently it was the first check they had me look at.
Part of the problem with the T/C design is that the extractor pushes the rear of the casing up against the top of the chamber, which does nothing to improve the alignment of the bullet to bore axis. This also explains why expanded cases have a noticeable lopsided shape above the web of the case. And also why it is important to full length re-size your brass.
T/C also informed me to shoot flat based bullets, as that's what their barrels prefer. *sigh*
When I called back to T/C to let them know of 20 fired factory Winchester cases I had, they all measured .470, with one at .471" They stated that because calipers have a +/- .001 accuracy, that the .471 could very well be .470". I think I confused him though when I asked if it was then possible the .470" cases could be .471" and the .471 was a .472." He paused for a second, put me on hold and then came back and said that since all but one was .470" that the one that measured .471" was probably just a piece of bad brass. It was like I was talking to "Raj" in India, but without the accent.
The overall impression I took away was that while T/C was more than happy to sell me a barrel they don't want anything more to do with it after it leaves the store.
I've got some more loads to work up and try sending down the barrel. If it doesn't behave I may try rechambering to a 6mm-284.