I have been hunting whitetails with the same 308 rifle for 10 years at that same time i bought my rifle my hunting companion bought a 270. The first 2 years my buddy used that 270 and it worked great for whitetails then he trades it off for a 30-06. No big deal I think I would have traded that savage 270 off for that sweet winchester 30-06 too. He hunted with that 30-06 for one year decided the recoil was to much and traded it off for a 308. I figured ok 308 is another fine whitetail cartridge. he hunted with it for 2 seasons then put it up and began using a 35 rem after the first season he decided it didnt have the range he wanted and sold it and went back to the 308 and used it for 3 more seasons. He never had any trouble killing whitetails with any of those calibers, then last year he trades off his 308 for a 7mm rem mag. I asked him why he needed a 7mm rem mag when all he ever hunts is whitetails in missouri and the average shot is 100 yards or less and all the other calibers he used worked just fine, he answered "Well I dont know just figured I needed the extra power for those big northern missouri bucks just incase I have to shoot across a corn field". I said well whatever floats your boat, all that 7 mag is gonna do is empty your wallet twice as fast as my 308 does me. Then he adds " Well honestly I actually just liked the gun it felt right and the gun store only had it in 7 mag, I didnt really give the 7 mag much thought just figured it wouldn't hurt to have the extra power. That season he shoots a nice 8 point at about 40 yards which ran practically into the next county I'll never forget how long we tracked that darn deer took us nearly 3 hours to find it , I ended up shooting a decent 7 point thought it was a 8 point across a cornfield about a 160-170 yard shot with my 308 that deer after being hit took several staggering steps then fell over dead.

My buddies deer was hit at such a angle that the bullet entered just behind its left shoulder and exited out the right tender loin (the best meat) bruising both loins the only vital that was hit was the left lung and some bone fragments hit the liver but not damaging the liver enough for a quick hemerage. My deer was hit just behind its left shoulder but the angle was just right sent bone fragments into both lungs and the bullet had a direct hit into the heart and the bullet exited just below and in front of the right shoulder.

Sure the magnums help on larger game ( elk, moose, brown bear etc) with extended range shots 300+ yards, but once again it boils down to shot placement. I dont care how big or powerfull your gun is, if you dont put that bullet in the right place,it doesnt matter. you may aswell shoot whatever animal you are hunting in the butt with a 22 long rifle if you first wont take the time to learn how to make good shots.