I disagree with Mr. Hawks whole heartedly! A 300 win mag or weatherby or whatever mag will do everthing a 30-06 does better and then some.. It shoots flatter, hits harder, 300 win mag argueably a more accurate round (that's one reason military snipers use it). Mr. hawks forgets that animals are killed by the effect of the energy transfer from the bullet to the critter aka hydrostatic shock. I can take a longer shot, an off angle quartering shot, etc and know that with a 200 gr bullet at 3050fps I can punch thru a lot of animal and deliver a lot of energy. Go try that with a 243, 270 I want to see you tear thru a ton of gut to get to the lungs at a quartering away shot on a big animal just not happening. In "real life" hunting you don't always get those perfect broadside volleys and with more gun in my hand I feel confortable taking less than ideal shots. So for my money if you can handle a 300 mag (or bigger) then why not use it? If you cant then shoot something less, shoot it well and be happy.
My basic principal my Daddy taught me many moons ago is son dead is dead hit em hard with the biggest stick you can and I don't care if you waste a little meat just make em dead!