I don't know the twist, but both my plain x5 and legion x5 are noticable more accurate with 124g bullets compared to 147g and 150g (syntech). all factory ammo. for me at 15 yards the difference is either a ragged hole with all the bullet holes touching, or with the heavier bullets you see the grouping open up and more of the holes not touching. Sent from my SM-N950U using Tapatalk