If I wanted an all around good caliber for target, squirrels and small whitetails, I'd go with a .40, if it met the legal minimum caliber where I was hunting, and if the deer were smallish, and the range likely to be 50 yds or less. If the gun were dedicated to deer hunting, the deer weren't smallish, and the ranges might be up to 100 yds, I'd go with a .50.