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A 1:8 twist let's you shoot higher b.c bullets which will come into effect after around 300 yards. To go with it a dialable scope to dial out error.
A 1:12 is relying on fast flat shooting light...

223 1:8 twist.
It depends on how far you want to shoot. If max 200 either calibre will do. But personally I wouldn't go lower than .224. Rabbits and the likes are small. high magnification scopes...