So the cassette slides on fine, but the lockring is ever so slightly too big and isn't taking onto the thread of the freehub. This seems odd as I'm confident the hub is a Chorus 9 speed and this is my lockring.
Campag changed the thread sizes of their lockrings somewhere around the transition from 8 to 9 speed. So some 9 speed freehubs come in the old size, some in the new.
I've probably got some knocking around, let me have a look.
So the cassette slides on fine, but the lockring is ever so slightly too big and isn't taking onto the thread of the freehub. This seems odd as I'm confident the hub is a Chorus 9 speed and this is my lockring.