I wrote a long post on this two years ago after experiencing the same frustration with conflicting well-intentioned advice. The problem (if you can call it that) is that the 6BR just flat out shoots and has the longest neck making it VERY forgiving on freebore selection.
There are effectively two polar opposite "common" 6BR builds based predominantly on freebore, with a third less common option for mid-range bullet specific shooters.
1. Slow twist (12-14) with short freebore (zero - 0.060)
2. Fast twist (7.5-8.5) with long freebore (0.080 - 0.135)
3. Medium twist (9-12) with short, medium, or long freebore dependent on bullet selection.
IMHO, the number one variable will be whether or not you plan to shoot flatback or boattail profile bullets. At all costs, don't listen to any freebore advice based on bullet weight. ***You care about base to ogive and boattail dimensions.*** This is the single biggest factor when selecting a reamer. The Berger 87 VLD can easily be shot in a zero freebore rifle of 10 or faster twist, but the 80 or 88 Flat backs will require as much as 0.080-0.140" more freebore to seat to the same position in the neck. As obvious as it may sound, 80 grainers with or without the boattail, will seat as differently as the boattail length.
Like other folks above, I had superb results with the 68 grain flat backs in my 8.8 twist Brux, even though it was custom built to shoot the 87 and 95 VLDs (I wasn't planning to shoot past 350 yards). If I had it to do again, I would pick a competition class & distance, then pick a custom bullet weight class & profile, and then the appropriate twist & freebore combo.
There is no one do-it-all solution because the short/light bullets and the heavy/long bullets are just too different.
Let us know what you decide and how it works out.
