The 1:7 twist is for longer heavier bullets ie; 69gr on up to the 80gr. The 55gr bullets will shoot from the 1:7 without doing any damage but your accuracy could suffer. I had a hard time with accuracy with the lighter bullets out past 200yds so I use the 69gr Sierra match king andthe problemwas solved. Thematch king bullets are a hollow point with a thin jacket andexplode when entering an animal. I thinkyou would like the results and the accuracy more than with the 55gr bullets.