My 6BR is a 26" 1-8 twist and with 30.5 gr. Varget behind 105 Amaxs it gives me 2830. I also have a load with 105 amaxs using 29.5 grs. H4895 for 2850 fps, it's as accurate as the Varget load. CCI 450's are about all you'll ever want for primers. As efficient as the case is I'd think 2700 would be easily doable out of a 20" 8 twist.
I love the 6BR, it's basically my definition of magic. Easiest round to make shoot I've ever messed with. Low blast, low recoil, accurate as all get out. It's only downside is feeding, if the montana action will feed it okay then it'll be a dandy.
