didn't know.308's were so effn powerful! I don't know much about ammo, but my neighbor has a 300 magnum that shoots damn hard!
.308 is sorta a baseline standard that other 30 cal rounds are measured by. (Well, that and the 30.06)
Obviously there are a shitpile of specialty rounds like the 300 Win/Mag, .338 Lapua etc that can do more, but if you go to a 600 yard high power rifle competition (No scope mind you) everyone is using .308.
I, personally, can get a consistent 7-8 inch grouping
without a scope at 600 yards using a Remington 700, and while I'm pretty good, I'm not a regular competitive shooter anymore. (Been three years or so.)
With a scope and knowing what you're doing, I can get the same groups at 850 yards with no problem, and 900 on a good day. At 900 though you're facing too many wind/drop/energy loss variables to be sure every time. the 7.62x51 has less power so not quite as good.
Basically what I'm saying is - I'd rather be
great at a round like .308/7.62x51 than only
good at a .338 Lapua or .300 Win Mag because I can't afford to shoot the things nearly as often.
Also, emergency situations require not the best, but the most commonly used goods.