1-9 twist
I have 199's and looked heavily at them also. They're a good option. But all Hammer does with their heavier bullets in add length to the shank to add the weight. So I strictly look at impact velocities with hammers. Because that shank is penetrating DEEP no matter what.
I'm shooting the 181 HH's great too, but going to try the 199's for the edge in BC. Also, if I remember correctly, looking at everyone's results, it seems like everyone manages to get the 199's shooting just as fast as the 181's.