I chopped my HMR in for a .222 in the end, I reload for .243 so was easy to start reloading for another CF, added bonus is that it is Muntjac legal, also much more effective on Fox.
I don't shoot 30 - 40 rabbits a night as per the OP, nor have I calculated the exact cost of the .222 reloads, I would guess 40p each depending on brass used. What I can say is that the gun is very accurate and I am much more confident of putting the round where I am aiming compared to the HMR's I owned.
yes mine is for rabbits and I want something to eat for my 30p shot