I cannot for the life of me imagine why they's say such a fool thing! I knew a doctor's wife once in Fairbanks Alaska who used to kill large bears with a .270 WIN using the 150-grain Nosler Partition bullet at a MV of 2800 FPS, usually with only one shot.

For many years, the heaviest brown bear taken in Alaska, which weighed in the vicinity of 1,600 pounds, was killed by a fellow named Harold McCracken around 1916 with a Model 95 Winchester in .30/40 Krag caliber.

So anyone who says a .300 Magnum won't kill big bears is full of it. The type of bullet one uses and shot placement are a lot more important than bullet diameter!