Actually, I've successfully hunted rabbits with a Ratcatcher producing a reliable 8.5fpe and it killed perfectly with accurately placed cranial shots at 25 yards, occasionally 30 yards.
Admittedly, I prefer 11fpe or a tiny bit more.
With the Weihrauch springers I've owned, once they are well 'run in', I've never even contemplated having them tuned as they go off so sweetly (in .22) that it seemed unnecessary. Can't beat pellet on pellet through a springer at 35 yards!
Don't let me put you off though - I imagine a tuned HW is sublime
cheers and happy hunting,
Duncan