.45 will do just fine. I use a custom Jp Beck .45 flinter. I have killed numerous whitetail with it. 2 seasons ago now I took one buck and 2 does with it within 3 weeks. all three were clean shots cutting a rib on the way in through both lungs top of heart at breaking bone on the way out with the bullet lodging under the hide of the opposite shoulder. All three round ball were recovered. All of them ran no more than 30 yards before they dropped over.
Many will give you the bigger is better story and that you should use nothing smaller than a .50 cal but I am with Rost495. Placement Placement Placement.
