A few years ago I shot a Swedish fallow deer, about the size of a nice whitetail, with a 6.5x55 using a handloaded 156 gr Norma Vulkan bullet. It was probably overkill. Of course the bullet sailed right on through and wasn't recovered, but the deer dropped in his tracks like he'd been electrocuted. I hunted quite a bit in Norway at the time, and the 6.5x55 was highly regarded. In fact, I think most Norwegian moose are still taken with 6.5 bullets.