Sorry to dissapoint you Sean,but your theory is flawed. Yes, a .308 bullet is slightly bigger than a .284,but the .284 will have better sectional density than a .308. What is SD? SD is basically a bullets ability to penetrate,the higher the bullets SD,the more it will penetrate.

Lets use the the Win. Fail Safe load. The 06 with 180gr,will have a SD of .271. The 7MM with 175gr will have a SD of .310. If you start both these out at 3000fps, hit an animal in the same location the .284 will out penetrate the .308. On animals like deer or pronghorns,it won't matter either way,you'll likely shoot right thru either one. step up to elk or moose ,and you'll need more penetration,I'd go with the .284 every time.Even a 160gr 7mm will probably out-penetrate a 180gr 06. SD of a 160gr 7mm is .283.

Your right about the velocity of magnums,only if you are shooting lightweight bullets at close range. Then you have a chance of the bullet "blowing up". The higher the velocity the greater the chances of that happening.Then you get little penetration.

That's the beauty of magnum's. You can load a heavier bullet than a "standard" round and get the same velocity. Heavier bullets and more velocity= more "oomph"