I will go out on a limb and agree with JamesB that the 243 SHOULD be the minimum legal firearm. In SD you can shoot deer with a 222 if you want, not that I reccomend it. I have shot a few deer with 60gr Nosler Partitions out of my 223, and I DO NOT reccomend it. All shots were placed perfectly, and every deer ran off not showing any signs of being hit. They ran anywhere from 50-250 yards then tipped over. All deer I have shot with my 243 have been anchored on the spot but one, and that one only went 40 yards or so. I have shot probably 20 deer personally with a 243, and I have 3 buddies that use them exclusively and have had no incidents of wounding/losing deer with any of them.