I’ve made fun of little bitty 243’s for years but that is what I bought for my son/grandson to hunt our little 115-150 lb California Pacific Mule deer and almost any bullet will work well up close & out past 300 yards. Southern whitetail won’t be any more challenging. I think it’s hard to beat a Nosler Ballistic tip for DRT deer. I’ve always used a 7 mag but the 243 results are similar.