"Best deer caliber" for Muleys and Blacktails in my case. I just made 2 lists, 1- rifles of mine capable of ethically and legally hunting deer in Oregon, and 2- handgun calibers that I currently have and can or have hunted deer with. Rifles from 223 to 460 - 16 cartridges, and handguns from 223 to 460. For example, 30 years ago I handgun hunted deer with a 357 maximum blackhawk and a scoped 223 Contender. Interestingly, exactly in the center of each list are the calibers that I hunt deer with the most. Rifle - 308. My go-to Rifle is my Savage 99f. Handgun 357 and 44 magnums. S&W 686+ pro 5", Ruger Super Blackhawk 7 1/2" (I wish it was stainless since we moved to the coast.)