Chasseur,

Stabilization of a bullet depends on both twist and velocity. Even if the 320's stabilize enough to be accurate on paper, if the twist is not fast enough, they can destabilize inside an animal. I am not saying they will, but since a 9.3 x 74 is built for 286 grain bullets, it is something to consider and experiment with before pinning the success of a hunt on the 320 grain bullets.