Well Mr Hill, I won't say "I told ya so".....but -------
If you need some better elk ammo just let me know. My offer will stand next year too.
You will find that "cup and core" bullets are fine for elk IF the cup is thick enough. In most .308" diameter bullets I know of, that means 180 grain and heavier, but not all. I have had seen good results with Remington Core Lokt in 165 gr, and their 180 do well too. So do the Winchester 180s and even their 150 gr power points, but a fully expanded 150 gr 30 cal is about 55-58 cal in frontal area, and at about 125 grains (after shedding 25 grains in it's journey through the elk) they hold together well, but sometimes don't get out the other side.
I have never stopped or seen stopped a 150 grain Remington 270 in an elk however. I believe the thicker jacket is a big part of the answer, and also the fact that a fully expanded 270 is about 50-52 cal and it's just enough smaller that the frontal resistance is slightly less, so it penetrates more. That's just my guess as to why I have not ever seen an elk stop one, but the part that is not theory is that they go through elk even when I have hit heavy bones That a fact.
Also keep in mind the solid expanding bullets (Xs and GMXs) made by Barnes and Hornady as well as the Partitions made by Nosler.
I have 42 years of elk hunting behind me. I have killed a lot of them myself and seen probably 5X more killed by other hunters, with all kinds of bullets from many different guns. I speak from experience, not theory.
Today we have more good choices of elk bullets then we ever have in the last 100 years.
In my opinion as both a hunter and an ex-guide, any bullet/cartridge that doesn't exit the elk is not what you want to hunt them with, and with a 308 Winchester there are quite a few loads that will give you good exits and bone-breaking potential, so there just is no reason not to use them.
Happy hunting and good luck for many years.