Out of curiosity, I ran the numbers for this bullet through Berger's stability calculator -- a value of 1.5 or greater is what they suggest as adequate stability. They give 1.44 for this bullet in a 1:8 and 1.89 for a 1:7 twist. It may be that your barrel doesn't like that bullet.
I found the sweet spot in my 28" - 1:7 barrel with the bullet touching the lands.
I found the sweet spot in my 28" - 1:7 barrel with the bullet touching the lands.