A friend of mine owns a gun shop that specializes in semi-custom rifles and high-end optics. When he goes hunting he's got the latest magnum caliber and a scope/rifle combo that's about as good as it can be in practically every respect.
His son shoots a .260 (basically a short action 6.5x55--6.5-08 to be precise). Certainly nothing special in the muzzle velocity department--no one would call it a magnum by a long shot.
I've been in the shop more than once when he was ranting that his son's deer always dropped where they were shot while he always had to track his...
I think that more people lose deer by shooting a rifle with recoil/blast that scares/hurts them than they lose because they're "under-gunned." The recoil/blast cause flinching and inadequate amounts of practice. That has exactly the expected results.