i think the best deer caliber is whatever u can shoot accurately enough and put it where it counts Be it a 223 or a 338 if you're accurate with it and feel comfortable with it and its adequatethan thats the best deer caliber for you. Everyone is different and everyone has different needs and desires so there is no best caliber for everyone. My personal preference for deer is a 6mm remington. My 223 has accounted for alot of deer though also. It's all in what you're comfortable with within legal and ethical means.