I have killed deer in MO with both the 264 WM and 6.5 WSM, they are identical ballistically. I think the 6.5 mm diameter is ideal for whitetails. The long high BC and high SD bullets buck the wind well and penetrate very well. Recoil is not bad at all with either cartridge with a 130-140 gr bullet. Of course, the 280AI is a cool round as well. Then there is the 6.5-06AI, the 25-06AI......
The critters have to win every time, I only have to win once.
NRA Life Member