I personally wouldn't even attempt a 50 for hunting. A friend of mine used a 338 Win mag on a little buck last year and all the hide was completely jerked loose on the opposite side. It was basically skinned already. It wasn't a good hit, so he didn't even have a good clean kill.
I have never seen the purpose for these big rifles and this just sealed it for me.
Anyone that thinks you need a 338 or bigger for any game in N America (or Africa for that matter), needs to go back to the targets and practice for a while. If you need something that will knock em down even if you hit them in the leg, apparently you need more practice.
In my humble opinion, anything above 30 cal is overkill.
Thats just my opinion and I know that many will disagree.