I have a 6mm BR rifle with a 1 in 14" twist. It will stabilize 55 through 70 grain bullets very well. I picked a 14" twist as the rifle is a varmint gun and shots are under 400 yards for the most part. I would not pick that twist again. However, I would not recommend that slow a twist. I would go with a 1 in 9" twist. It's hard to over stabilize a bullet, but easy to have too slow a twist.
