Alot of rabbit shooting is done in low light levels ( dusk / dawn ) and rabbits are small and tend to blend in low light.
since you only have 12fpe, you must be more clinical than someone using a rimfire, ( with 100fpe ).
All im saying is pay for better glass - you rarely regreat buying quality-
Lastly, you dont have to spend a £1000 on a scope , but a £100 scope wont have the same light garthering abilities .... Sirslots