I've been shutting things down, here, to take off for a month to South Jawgia--all my books are back in the loading room. But aren't these "Bench Rest" wildcats sorta long in the neck?
I'll cop out and go back to "Magic".
But just for the heck of it: When I resize my '06 cases, I only resize about 1/2 to 2/3 of the length of the neck. Isn't this about the same deal as the shorter neck on the .308?
Reaming and turning of the case neck would ensure uniform thickness, and concentricity with the bore even before loading. Next, make sure the new bullet is concentric with the bore. These factors would seem more important that the actual length of the neck.
Obviously, the factories do a pretty good job, already, with their brass. I've never done these extra steps, and I regularly get three-shot groups inside of 3/4" (occasionally, 1/2"), and I have gotten 10-shot groups inside of an inch. And that's with a pretty-much standard-sized barrel, not a heavy. And no notable interval between shots, either.
Magic, dammit, magic!
Art