I subscribe to similar thinking as cty100 as it relates to energy transfer. Shooting deer with my .300WSM is effective, but the bullet is moving so quickly, it does not trasfer all its energy to the animal. I also have a .243 and .308 which work great on deer. Perhaps the utlimate in knockdown power has been the .12ga with slugs and my.44mag shooting 240gr bullets. They transfer 100% of their energy and the deer is usually taken off its feet.