I have 2 scopes for the 9,3 a 2.5-8 Leupold with the heavy duplex, and a Swarovski 1.5-6x42 with the circle dot reticle. Both in the Chapuis pivot mounts.

On the 400 I have a S&B 1-4 with the illiminated reticle, in claw mounts.
I highly recommend you put a scope in QD mounts on your 400.

I can do anything with my sciped 400 double that I could do with a scoped 416 Rem Mag bolt rifle.