Originally Posted by
Tahr
Red deer aren't that hard to kill with a well placed shot. Fallow even easier. You seem to understand its limitations, so go for it.
I've shot enough with Remington 55 grn factory ammo and Winchester 64 grn to know that it works. They will shoot fine through your 1:12 because they are not long bullets, but you might just want to check that the 64 grn factory actually does in your rifle. If it does, that's what I would use.
And as said above, the Norma Onyx should be a good factory loaded bonded bullet too. They are a stumpy little job so should shoot ok in your rifle's twist. I've only shot them at paper but they were accurate enough. I could give you a few to try if you PM me your address.
Hundreds of thousands of deer in NZ have been shot by the .222 and .223. You should be able to add a few more.