My experience with the 6BR has been wide, having used 1/8", and 1/7.5" twist barrels. I have used bullets from as light as 88 gr Berger FB up to the 115 gr Berger VLD.
Having said that, the reamer used has a longer than usual throat, allowing a longer seating of the bullet, and therefore accepting a smithen more powder, without disturbing the pressure monster.
Accuracy at 1,000 yds is excellent, at a speed borthering 2,900 fps. The Sierra 107s and Lapua 105s will do 2,950 fps. I could have gone for the BRX instead, but decided to play with the reamer, and not have to deal with additional dies, brass, necks, etc. It worked.
Barrels with 1/7" are theoreticaly best handling 115 VLDs. I agree and not. Yes, they do fly amazingly well, and they will also occasionaly dissapear when pushed at maximum revolutions. The 1/7.5 seems to do a better job at keeping things in check.
I have also tested this with several 6CM barrels, and the 1/7" will always surprise me (at the worst moment) with a "did not arrive" notice. Not good. The 1/7.5 has proven better so far. Reducing the speed in the 1/7 " barrel helped a lot, but killed the intention.
More to come,
Andy,