The .223 works, just has a small sweet spot on deer. If you go too big though, the sweet spot gets small too, because almost anywhere you hit there will be damage to the meat. Personally, I prefer a 25-06, its just the right mix of knockdown power, speed, and trajectory for me. But I've shot deer with a .243, 300 win mag, .308, .223, 30-06, they all work, and everyone's preference is personal. I prefer to big over too small, because I would rather waste meat than leave an animal wounded and alive.