Bullet rifling simulation

I have a (RigidBody) bullet simulation with the following parameters:
Velocity at launch;
Torque at launch;

The velocity changes over time according to parabolic ballistics, ricochets, etc…
The rotation of the bullet may change over time according to angular drag.

I need the axis of rotation of the bullet to “look at” the velocity of the bullet so that it always rifles through the air on an axis parallel to its motion.

Many thanks!

transform.forward is the axis you are asking for.