I think you are running into the RPM threshold. A too soft bullet will not shoot accurately if you twist it too hard. Also you need to reduce the jump to the rifling to as small a distance as possible. I prefer to shoot cast bullets jammed into the rifling. Bore riding bullets need to have the bore riding nose to be in contact with the lands. You don't tell us what your land and groove dimentions are for this new rifle and how long of a jump to the rifling you are setting. 1 to 10 is way more twist than you need for a 170 gr. bullet at 2000 fps. Your rifle design is not good for a hunting rifle where you want to use a soft bullet at reasonable hunting rifle velocities. I suggest you trade it off to someone how will shoot j words and look for a more appropriate gun.
Tim