Over the past 30 years I have taken many whitetail with a 243 using 100 grain bullets. Every single time they were dead before they hit the ground. Last year, at the behest of a friend of mine, I used his 7MM mag. (I think he thought it needed good medicine on it). Indeed, I put a bullet through the heart of a nice buck at just under 400 yards. Although it did the job, the buck still ran about 40 yards (albiet downhill) before he piled up at the bottom of an arroyo. Now, my 243 weighs about 3 lbs. lighter and the ammo is cheaper. Moral of this story: sometimes you can use too much gun.
Jim Sparling